Bepridil opens the regulatory N-terminal lobe of cardiac troponin C

Yu, Li; Love, M.L.; Putkey, John A.; Cohen, Carolyn

doi:10.1073/pnas.090098997

Cited by 73 publications

(122 citation statements)

References 33 publications

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“…Thus, the current observations explain the discrepancies between earlier studies of levosimendan binding to cTnC. Our results suggest that the primary binding site is located in the regulatory domain (cNTnC) of cTnC and that there are two secondary binding sites at the C-terminal half of cTnC possibly analogous to the case of three bepridil molecules binding to cTnC A-Cys (33). Likewise, levosimendan may contribute to the opening of the regulatory domain.…”

Section: Discussioncontrasting

confidence: 57%

See 1 more Smart Citation

Binding of Levosimendan, a Calcium Sensitizer, to Cardiac Troponin C

Sorsa

Heikkinen

Abbott

et al. 2001

Journal of Biological Chemistry

134

109

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Levosimendan is an inodilatory drug that mediates its cardiac effect by the calcium sensitization of contractile proteins. The target protein of levosimendan is cardiac troponin C (cTnC). In the current work, we have studied the interaction of levosimendan with Ca 2؉ -saturated cTnC by heteronuclear NMR and small angle x-ray scattering. A specific interaction between levosimendan and the Ca 2؉ -loaded regulatory domain of recombinant cTnC C35S was observed. The changes in the NMR spectra of the N-domain of full-length cTnC C35S , due to the binding of levosimendan to the primary site, were indicative of a slow conformational exchange. In contrast, no binding of levosimendan to the regulatory domain of cTnC ACys, where all the cysteine residues are mutated to serine, was detected. Moreover, it was shown that levosimendan was in fast exchange on the NMR time scale with a secondary binding site in the C-domain of both cTnC C35S and cTnC A-Cys . The small angle x-ray scattering experiments confirm the binding of levosimendan to Ca 2؉ -saturated cTnC but show no domain-domain closure. The experiments were run in the absence of the reducing agent dithiothreitol and the preservative sodium azide (NaN 3 ), since we found that levosimendan reacts with these chemicals, commonly used for preparation of NMR protein samples.The number of patients suffering from heart failure is increasing along with the aging of population. Calcium sensitizers have been proposed as a treatment for congestive heart failure since they exert a positive inotropic effect without increasing the intracellular calcium concentration (1). Levosimendan, a potent calcium sensitizer that improves the force development of the muscle contraction without increasing the cytosolic Ca 2ϩ ion concentration (2), was discovered using troponin C as target protein.Troponin C (TnC) 1 is responsible for the contraction trigger in the muscle. It belongs to the family of calcium binding EF-hand proteins and consists of two domains. The N-terminal half (NTnC) is responsible for the calcium-dependent regulation of the contraction, and the C-terminal half is a structural domain always loaded with divalent cations under physiological conditions. Troponin C interacts with troponin I (TnI), and this interaction is modulated by the binding of calcium. Studies of skeletal troponin C, a homologous protein, show that a hydrophobic patch is exposed in the open conformation of the calcium-loaded regulatory domain, which is a binding site for TnI (3). This has also been proposed to be a potential binding site for calcium sensitizers (4, 5). Contrary to skeletal troponin C, the binding of Ca 2ϩ to cTnC does not induce an opening of the conformation. Consequently there is, in vitro, no exposure of a hydrophobic region (6 -9). The simultaneous binding of cardiac troponin I and Ca 2ϩ to cNTnC, however, opens the structure of the N-terminal domain (10, 11). This structural and functional difference between TnC in skeletal and cardiac muscle is still to be clarified.Levosimendan has been...

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Section: Discussioncontrasting

confidence: 57%

“…bepridil, EMD57033, and trifluoperazine (24, 32)). Recently, it has been shown by x-ray crystallography that the structure of cNTnC opens in response to bepridil binding (33). Three bepridil mol- FIG.…”

Section: Binding Of Levosimendan To (Ca 2ϩmentioning

confidence: 99%

Binding of Levosimendan, a Calcium Sensitizer, to Cardiac Troponin C

Sorsa

Heikkinen

Abbott

et al. 2001

Journal of Biological Chemistry

134

109

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“…All of these studies agree that binding of bepridil requires site II in cTnC to be occupied by Ca 2+ . The X-ray structure of cTnC·3Ca 2+ ·3bepridil provided detailed structural data on the interaction of cTnC and bepridil [57]. In this structure, two bepridil molecules pull the N-and C-domains together to result in a compact structure for cTnC while a third bepridil appears to stabilize an 'open' cNTnC conformation by binding to the center of the hydrophobic pocket, much like the switch region cTnI [147][148][149][150][151][152][153][154][155][156][157][158][159][160][161][162][163] .…”

Section: Bepridilmentioning

confidence: 99%

Interaction of cardiac troponin with cardiotonic drugs: A structural perspective

Robertson

Sykes

2008

Biochemical and Biophysical Research Communications

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Over the forty years since its discovery, many studies have focused on understanding the role of troponin as a myofilament based molecular switch in regulating the Ca 2+ -dependent activation of striated muscle contraction. Recently, studies have explored the role of cardiac troponin as a target for cardiotonic agents. These drugs are clinically useful for treating heart failure, a condition in which the heart is no longer able to pump enough blood to other organs. These agents act via a mechanism that modulates the Ca 2+ -sensitivity of troponin; such a mode of action is therapeutically desirable because intracellular Ca 2+ concentration is not perturbed, preserving the regulation of other Ca 2+ -based signaling pathways. This review describes molecular details of the interaction of cardiac troponin with a variety of cardiotonic drugs. We present recent structural work that has identified the docking sites of several cardiotonic drugs in the troponin C -troponin I interface and discuss their relevance in the design of troponin based drugs for the treatment of heart disease.

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“…Recently, it has been shown, in vitro, that BPD itself could induce an opening of the N-lobe of the cardiac isoform (similar to the N-lobe of 4Ca 2+ -skeletal TnC), and a stabilization of this N-lobe (Li et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

The role of the Ca²⁺ regulatory sites of skeletal troponin C in modulating muscle fibre reactivity to the Ca²⁺ sensitizer bepridil

Kischel¹,

Bastide²,

Potter

et al. 2000

British J Pharmacology

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1 The Ca 2+ -sensor protein troponin C (TnC) exerts a key role in the regulation of muscle contraction, and constitutes a target for Ca 2+ sensitizer compounds, such as bepridil, known to increase its apparent Ca 2+ a nity. Moreover, bepridil has been reported to exert a di erential e ect in slow and fast skeletal muscle ®bres, which express the slow/cardiac and fast TnC isoform, respectively. 2 The role of the TnC isoform in establishing the di erential e ect of bepridil was assessed in slow soleus and fast tibialis rat skinned ®bres, by extraction of endogenous TnC and consecutive reconstitution with either slow or fast recombinant TnC. A mutant (VG2), lacking the regulatory site II, was also used to distinguish the role of each regulatory site. 3 Fast tibialis ®bres reconstituted with cardiac TnC exhibited a typical slow bepridil reactivity, while slow soleus ®bres reincorporated with fast TnC displayed a typically fast reactivity to bepridil. These results indicated that the di erential e ect of bepridil in slow and fast ®bres is related to the TnC isoform predominantly expressed in a ®bre. 4 Experiments with the VG2 mutant demonstrated that BPD can achieve an increase in the Ca 2+ a nity in the absence of a functional site II. Thus, site I was necessary for the BPD e ect to be independent of the Ca 2+ concentration. Moreover, the amplitude of the reinforcement in the Ca 2+ a nity, induced by the binding of bepridil to the TnC molecule, is dependent on the number of functional regulatory sites, the larger a nity reinforcement being detected when only one regulatory site (either site I or II) is functional.

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Bepridil opens the regulatory N-terminal lobe of cardiac troponin C

Cited by 73 publications

References 33 publications

Binding of Levosimendan, a Calcium Sensitizer, to Cardiac Troponin C

Binding of Levosimendan, a Calcium Sensitizer, to Cardiac Troponin C

Interaction of cardiac troponin with cardiotonic drugs: A structural perspective

The role of the Ca²⁺ regulatory sites of skeletal troponin C in modulating muscle fibre reactivity to the Ca²⁺ sensitizer bepridil

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Bepridil opens the regulatory N-terminal lobe of cardiac troponin C

Cited by 73 publications

References 33 publications

Binding of Levosimendan, a Calcium Sensitizer, to Cardiac Troponin C

Binding of Levosimendan, a Calcium Sensitizer, to Cardiac Troponin C

Interaction of cardiac troponin with cardiotonic drugs: A structural perspective

The role of the Ca2+ regulatory sites of skeletal troponin C in modulating muscle fibre reactivity to the Ca2+ sensitizer bepridil

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The role of the Ca²⁺ regulatory sites of skeletal troponin C in modulating muscle fibre reactivity to the Ca²⁺ sensitizer bepridil