The Effects of Phosphorylation of Cardiac Troponin-I on Its Interactions with Actin and Cardiac Troponin-C

Al-Hillawi, Eman; Bhandari, Dhan G.; Trayer, Hylary R.; Trayer, Ian P.

doi:10.1111/j.1432-1033.1995.tb20347.x

Cited by 33 publications

(3 citation statements)

References 45 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This could reflect the release of the N-terminal extension from a binding site on TnC and possibly movement toward a binding site on the C-terminal region of TnI for the phosphorylated N-terminal extension. Bisphosphorylation of TnI produces a slight decrease in the affinity of TnI for TnC ( , ). This reduction in affinity could arise directly from the loss of the binding contribution from the phosphorylation switch although there is evidence that phosphorylation of the extension alters the affinity of the C-terminal region of TnI for TnC ().…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Interaction between the N-Terminal Extension of Human Cardiac Troponin I and Troponin C

et al. 2004

Self Cite

View full text Add to dashboard Cite

The N-terminal extension of cardiac troponin I (TnI) is bisphosphorylated by protein kinase A in response to beta-adrenergic stimulation. How this signal is transmitted between TnI and troponin C (TnC), resulting in accelerated Ca(2+) release, remains unclear. We recently proposed that the unphosphorylated extension interacts with the N-terminal domain of TnC stabilizing Ca(2+) binding and that phosphorylation prevents this interaction. We now use (1)H NMR to study the interactions between several N-terminal fragments of TnI, residues 1-18 (I1-18), residues 1-29 (I1-29), and residues 1-64 (I1-64), and TnC. The shorter fragments provide unambiguous information on the N-terminal regions of TnI that interact with TnC: I1-18 does not bind to TnC whereas the C-terminal region of unphosphorylated I1-29 does bind. Bisphosphorylation greatly weakens this interaction. I1-64 contains the phosphorylatable N-terminal extension and a region that anchors I1-64 to the C-terminal domain of TnC. I1-64 binding to TnC influences NMR signals arising from both domains of TnC, providing evidence that the N-terminal extension of TnI interacts with the N-terminal domain of TnC. TnC binding to I1-64 broadens NMR signals from the side chains of residues immediately C-terminal to the phosphorylation sites. Binding of TnC to bisphosphorylated I1-64 does not broaden these NMR signals to the same extent. Circular dichroism spectra of I1-64 indicate that bisphosphorylation does not produce major secondary structure changes in I1-64. We conclude that bisphosphorylation of cardiac TnI elicits its effects by weakening the interaction between the region of TnI immediately C-terminal to the phosphorylation sites and TnC either directly, due to electrostatic repulsion, or via localized conformational changes.

show abstract

Section: Discussionmentioning

confidence: 99%

Characterization of the Interaction between the N-Terminal Extension of Human Cardiac Troponin I and Troponin C

et al. 2004

Self Cite

View full text Add to dashboard Cite

show abstract

“…A similar B helix opening was observed without Ca 2+ binding to the N-domain in the binary complex. Phosphorylation of two serine residues (S23 and S24) in cardiac TnI causes a reduction in Ca 2+ binding affinity in the N-domain of TnC ( − ), indicating that the N-terminal region of TnI interacts with the N-domain of TnC. Small angle neutron scattering () and cross-linking () studies suggest the existence of this interaction.…”

Section: Discussionmentioning

confidence: 99%

Site-Directed Spin Labeling Electron Paramagnetic Resonance Study of the Calcium-Induced Structural Transition in the N-Domain of Human Cardiac Troponin C Complexed with Troponin I

et al. 2004

View full text Add to dashboard Cite

Calcium-induced structural transition in the amino-terminal domain of troponin C (TnC) triggers skeletal and cardiac muscle contraction. The salient feature of this structural transition is the movement of the B and C helices, which is termed the "opening" of the N-domain. This movement exposes a hydrophobic region, allowing interaction with the regulatory domain of troponin I (TnI) as can be seen in the crystal structure of the troponin ternary complex [Takeda, S., Yamashita, A., Maeda, K., and Maeda, Y. (2003) Nature 424, 35-41]. In contrast to skeletal TnC, Ca(2+)-binding site I (an EF-hand motif that consists of an A helix-loop-B helix motif) is inactive in cardiac TnC. The question arising from comparisons with skeletal TnC is how both helices move according to Ca(2+) binding or interact with TnI in cardiac TnC. In this study, we examined the Ca(2+)-induced movement of the B and C helices relative to the D helix in a cardiac TnC monomer state and TnC-TnI binary complex by means of site-directed spin labeling electron paramagnetic resonance (EPR). Doubly spin-labeled TnC mutants were prepared, and the spin-spin distances were estimated by analyzing dipolar interactions with the Fourier deconvolution method. An interspin distance of 18.4 A was estimated for mutants spin labeled at G42C on the B helix and C84 on the D helix in a Mg(2+)-saturated monomer state. The interspin distance between Q58C on the C helix and C84 on the D helix was estimated to be 18.3 A under the same conditions. Distance changes were observed by the addition of Ca(2+) ions and the formation of a complex with TnI. Our data indicated that the C helix moved away from the D helix in a distinct Ca(2+)-dependent manner, while the B helix did not. A movement of the B helix by interaction with TnI was observed. Both Ca(2+) and TnI were also shown to be essential for the full opening of the N-domain in cardiac TnC.

show abstract

“…Thus, the interactions of TnC with TnI and Ca 2+ are crucial for the Ca 2+ control of muscle. Early studies showed that β-adrenergic stimulation of contraction was associated with enhanced phosphorylation of TnI (England, 1976; Solaro et al, 1976), that TnI was bis-phosphorylated at serines 22 and 23 in the cardiac-specific N-terminal extension by PKA (Mittmann et al, 1990; Al-Hillawi et al, 1995; Ayaz-Guner et al, 2009) and that the primary effect of phosphorylation of TnI in vitro was reduced Ca 2+ -sensitivity and faster dissociation of Ca 2+ from TnC (Solaro et al, 1976; Robertson et al, 1982; Zhang et al, 1995; Dong et al, 2007). This can cause an increase in the rate of relaxation (lusitropic response) which is essential when heart rate is increased (Kentish et al, 2001; Layland et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Investigating the role of uncoupling of troponin I phosphorylation from changes in myofibrillar Ca2+-sensitivity in the pathogenesis of cardiomyopathy

Messer

Marston

2014

Front. Physiol.

View full text Add to dashboard Cite

Contraction in the mammalian heart is controlled by the intracellular Ca2+ concentration as it is in all striated muscle, but the heart has an additional signaling system that comes into play to increase heart rate and cardiac output during exercise or stress. β-adrenergic stimulation of heart muscle cells leads to release of cyclic-AMP and the activation of protein kinase A which phosphorylates key proteins in the sarcolemma, sarcoplasmic reticulum and contractile apparatus. Troponin I (TnI) and Myosin Binding Protein C (MyBP-C) are the prime targets in the myofilaments. TnI phosphorylation lowers myofibrillar Ca2+-sensitivity and increases the speed of Ca2+-dissociation and relaxation (lusitropic effect). Recent studies have shown that this relationship between Ca2+-sensitivity and TnI phosphorylation may be unstable. In familial cardiomyopathies, both dilated and hypertrophic (DCM and HCM), a mutation in one of the proteins of the thin filament often results in the loss of the relationship (uncoupling) and blunting of the lusitropic response. For familial dilated cardiomyopathy in thin filament proteins it has been proposed that this uncoupling is causative of the phenotype. Uncoupling has also been found in human heart tissue from patients with hypertrophic obstructive cardiomyopathy as a secondary effect. Recently, it has been found that Ca2+-sensitizing drugs can promote uncoupling, whilst one Ca2+-desensitizing drug Epigallocatechin 3-Gallate (EGCG) can reverse uncoupling. We will discuss recent findings about the role of uncoupling in the development of cardiomyopathies and the molecular mechanism of the process.

show abstract

The Effects of Phosphorylation of Cardiac Troponin-I on Its Interactions with Actin and Cardiac Troponin-C

Cited by 33 publications

References 45 publications

Characterization of the Interaction between the N-Terminal Extension of Human Cardiac Troponin I and Troponin C

Characterization of the Interaction between the N-Terminal Extension of Human Cardiac Troponin I and Troponin C

Site-Directed Spin Labeling Electron Paramagnetic Resonance Study of the Calcium-Induced Structural Transition in the N-Domain of Human Cardiac Troponin C Complexed with Troponin I

Investigating the role of uncoupling of troponin I phosphorylation from changes in myofibrillar Ca2+-sensitivity in the pathogenesis of cardiomyopathy

Contact Info

Product

Resources

About