Troponin I serines 43/45 and regulation of cardiac myofilament function

2002 ◽  
Vol 283 (3) ◽  
pp. H1215-H1224 ◽  
Author(s):  
W. Glen Pyle ◽  
Marius P. Sumandea ◽  
R. John Solaro ◽  
Pieter P. De Tombe
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
Fiber Bundles ◽  
Maximum Tension ◽  
Myofilament Function ◽  
Cardiac Myofilament ◽  
Myofilament Activation ◽  
Tension Cost ◽  
Mgatpase Activity

We studied Ca2+ dependence of tension and actomyosin ATPase rate in detergent extracted fiber bundles isolated from transgenic mice (TG), in which cardiac troponin I (cTnI) serines 43 and 45 were mutated to alanines (cTnI S43A/S45A). Basal phosphorylation levels of cTnI were lower in TG than in wild-type (WT) mice, but phosphorylation of cardiac troponin T was increased. Compared with WT, TG fiber bundles showed a 13% decrease in maximum tension and a 20% increase in maximum MgATPase activity, yielding an increase in tension cost. Protein kinase C (PKC) activation with endothelin (ET) or phenylephrine plus propranolol (PP) before detergent extraction induced a decrease in maximum tension and MgATPase activity in WT fibers, whereas ET or PP increased maximum tension and stiffness in TG fibers. TG MgATPase activity was unchanged by ET but increased by PP. Measurement of protein phosphorylation revealed differential effects of agonists between WT and TG myofilaments and within the TG myofilaments. Our results demonstrate the importance of PKC-mediated phosphorylation of cTnI S43/S45 in the control of myofilament activation and cross-bridge cycling rate.

Relaxin alters cardiac myofilament function through a PKC-dependent pathway

2009 ◽  
Vol 297 (1) ◽  
pp. H29-H36 ◽  
Author(s):  
Erynn E. Shaw ◽  
Philip Wood ◽  
Justyna Kulpa ◽  
Feng Hua Yang ◽  
Alastair J. Summerlee ◽  
...  
Keyword(s):  
Intracellular Signaling ◽  
Troponin I ◽  
Troponin T ◽  
Immunoblot Analysis ◽  
Inotropic Effects ◽  
Myosin Binding Protein ◽  
Myofilament Function ◽  
Cardiac Myofilament ◽  
Intracellular Ca ◽  
Myofilament Activation

The pregnancy hormone relaxin (RLX) is a powerful cardiostimulatory peptide. Despite its well-characterized effects on the heart, the intracellular mechanisms responsible for RLX's positive inotropic effects are unknown. Cardiac myofilaments are the central contractile elements of the heart, and changes in the phosphorylation status of myofilament proteins are known to mediate changes in function. The first objective of this study was to determine whether RLX stimulates myofilament activation and alters the phosphorylation of one or more myofilament proteins. RLX works through a variety of intracellular signaling cascades in different tissue types. Protein kinases A (PKA) and C (PKC) are two common molecules implicated in RLX signaling and are known to affect myofilament function. Thus the second objective of this study was to determine whether RLX mediates its myocardial effects through PKA or PKC activation. Murine myocardium was treated with recombinant H2-RLX, and cardiac myofilaments were isolated. RLX increased cardiac myofilament force development at physiological levels of intracellular Ca2+ without altering myofilament ATP consumption. Myosin binding protein C, troponin T, and troponin I phosphorylation levels were increased with RLX treatment. Immunoblot analysis revealed an increase in myofilament-associated PKC-δ, decreases in PKC-α and -βII, but no effect on PKC-ε. Inhibition of PKC with chelerythrine chloride or PKC-δ with rottlerin prevented the RLX-dependent changes in myofilament function and protein phosphorylation. PKA antagonism with H-89 had no effect on the myofilament effects of RLX. This study is the first to show that RLX-dependent changes in myofilament-associated PKC alters myofilament activation in a manner consistent with its cardiostimulatory effects.

Cardiac myofilament regulation by protein phosphatase type 1α and CapZ

2008 ◽  
Vol 86 (1) ◽  
pp. 70-78 ◽  
Author(s):  
Fenghua Yang ◽  
David L. Aiello ◽  
W. Glen Pyle
Keyword(s):  
Protein Phosphatase ◽  
Troponin I ◽  
Troponin T ◽  
Immunoblot Analysis ◽  
Intracellular Signalling ◽  
General Role ◽  
Myosin Light Chain 2 ◽  
Cardiac Myofilament ◽  
Myofilament Activation ◽  
Protein Phosphatase Type

Myofilament regulation by protein kinases is well characterized, but relatively little is known about protein phosphatase control of myofilaments. Increased protein phosphatase type 1 (PP1) activity observed in failing hearts underscores the need for investigation of this intracellular signal, including the elements that regulate its activity. The Z-disc protein CapZ controls protein kinase C (PKC) regulation of cardiac myofilaments, but whether this effect is specific to PKC, or CapZ plays a general role in intracellular signalling, is not known. We sought to determine how the α isoform of PP1 (PP1α) regulates murine cardiac myofilaments and whether CapZ influences PP1α-dependent regulation of cardiac myofilaments. Immunoblot analysis showed PP1α binding to cardiac myofilaments. Exogenous PP1α increased myofilament Ca2+ sensitivity and maximal actomyosin Mg2+-ATPase activity while dephosphorylating myosin binding protein C, troponin T, troponin I, and myosin light chain 2. Extraction of CapZ decreased myofilament-associated PP1α and attenuated the effects of PP1α on myofilament activation. PP1α-dependent dephosphorylation of myofilament proteins was reduced with CapZ extraction, except for troponin I. Extracting CapZ after PP1α treatment allowed most of the PP1α-dependent effects on myofilament activation to remain, indicating that CapZ removal modestly desensitizes cardiac myofilaments to dephosphorylation. Our results demonstrate myofilament regulation by PP1α and support the concept that cardiac Z-discs are vital components in intracellular signalling.

scholarly journals Pim-1 Kinase Phosphorylates Cardiac Troponin I and Regulates Cardiac Myofilament Function

2018 ◽  
Vol 45 (6) ◽  
pp. 2174-2186 ◽  
Author(s):  
Ni Zhu ◽  
Bing Yi ◽  
Zhifu Guo ◽  
Guanxin Zhang ◽  
Shengdong Huang ◽  
...  
Keyword(s):  
Growth Factor ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I ◽  
Site Directed Mutagenesis ◽  
Functional Assay ◽  
Protective Effects ◽  
Diabetic Mice ◽  
Myofilament Function ◽  
Cardiac Myofilament

Background/Aims: Pim-1 is a serine/threonine kinase that is highly expressed in the heart, and exerts potent cardiac protective effects through enhancing survival, proliferation, and regeneration of cardiomyocytes. Its myocardial specific substrates, however, remain unknown. In the present study, we aim to investigate whether Pim-1 modulates myofilament activity through phosphorylation of cardiac troponin I (cTnI), a key component in regulating myofilament function in the heart. Methods: Coimmunoprecipitation and immunofluorescent assays were employed to investigate the interaction of Pim-1 with cTnI in cardiomyocytes. Biochemical, site directed mutagenesis, and mass spectrometric analyses were utilized to identify the phosphorylation sites of Pim1 in cTnI. Myofilament functional assay using skinned cardiac fiber was used to assess the effect of Pim1-mediated phosphorylation on cardiac myofilament activity. Lastly, the functional significance of Pim1-mediated cTnI in heart disease was determined in diabetic mice. Results: We found that Pim-1 specifically interacts with cTnI in cardiomyocytes and this interaction leads to Pim1-mediated cTnI phosphorylation, predominantly at Ser23/24 and Ser150. Furthermore, our functional assay demonstrated that Pim-1 induces a robust phosphorylation of cTnI within the troponin complex, thus leading to a decreased Ca2+ sensitivity. Insulin-like growth factor 1 (IGF-1), a peptide growth factor that has been shown to stimulate myocardial contractility, markedly induces cTnI phosphorylation at Ser23/24 and Ser150 through increasing Pim-1 expression in cardiomyocytes. In a high-fat diabetic mice model, the expression of Pim1 in the heart is significantly decreased, which is accompanied by a decreased phosphorylation of cTnI at Ser23/24 and Ser150, further implicating the pathological significance of the Pim1/cTnI axis in the development of diabetic cardiomyopathy. Conclusion: Our results demonstrate that Pim-1 is a novel kinase that phosphorylates cTnI primarily at Ser23/24 and Ser150 in cardiomyocytes, which in turn may modulate myofilament function under a variety of physiological and pathophysiological conditions.

Transgenic incorporation of skeletal TnT into cardiac myofilaments blunts PKC-mediated depression of force

2001 ◽  
Vol 280 (3) ◽  
pp. H1011-H1018 ◽  
Author(s):  
David E. Montgomery ◽  
Murali Chandra ◽  
Qi-Quan Huang ◽  
Jian-Ping Jin ◽  
R. John Solaro
Keyword(s):  
Troponin I ◽  
Troponin T ◽  
Tension Development ◽  
Maximum Tension ◽  
Kinase C ◽  
Cardiac Myofilament ◽  
Skinned Fiber Bundles ◽  
The Impact ◽  
Pkc Activation

Protein kinase C (PKC)-mediated phosphorylation of cardiac troponin I (cTnI) and troponin T (cTnT) has been shown to diminish maximum activation of myofilaments. The functional role of cTnI phosphorylation has been investigated. However, the impact of cTnT phosphorylation on myofilament force is not well studied. We tested the effect of endogenous PKC activation on steady-state tension development and Ca2+ sensitivity in skinned fiber bundles from transgenic (TG) mouse hearts expressing fast skeletal TnT (fsTnT), which naturally lacks the PKC sites present in cTnT. The 12- O-tetradecanoylphorbol 13-acetate (TPA) treatment induced a 29% (46.1 ± 2.5 vs. 33.4 ± 2.6 mN/mm2) reduction in maximum tension in the nontransgenic (NTG) preparations ( n = 7) and was inhibited with chelerythrine. However, TPA did not induce a change in the maximum tension in the TG preparations ( n = 11). TPA induced a small but significant ( P < 0.02) increase in Ca2+sensitivity (untreated pCa50 = 5.63 ± 0.01 vs. treated pCa50 = 5.72 ± 0.01) only in TG preparations. In TG preparations, 32P incorporation was not evident in TnT and was also significantly diminished in cTnI, compared with NTG. Our data indicate that incorporation of fsTnT into the cardiac myofilament lattice blunts PKC-mediated depression of maximum tension. These data also suggest that cTnT may play an important role in amplifying the myofilament depression induced by PKC-mediated phosphorylation of cTnI.

α-Adrenergic response and myofilament activity in mouse hearts lacking PKC phosphorylation sites on cardiac TnI

2002 ◽  
Vol 282 (6) ◽  
pp. H2397-H2405 ◽  
Author(s):  
David E. Montgomery ◽  
Beata M. Wolska ◽  
W. Glen Pyle ◽  
Brian B. Roman ◽  
Jasmine C. Dowell ◽  
...  
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
Specific Inhibitor ◽  
Transient Increase ◽  
Phosphorylation Sites ◽  
Papillary Muscles ◽  
Reduction In Force ◽  
Actomyosin Interaction ◽  
Cardiac Myofilament

Protein kinase C (PKC)-mediated phosphorylation of cardiac myofilament (MF) proteins has been shown to depress the actomyosin interaction and may be important during heart failure. Biochemical studies indicate that phosphorylation of Ser43 and Ser45 of cardiac troponin I (cTnI) plays a substantial role in the PKC-mediated depression. We studied intact and detergent-extracted papillary muscles from nontransgenic (NTG) and transgenic (TG) mouse hearts that express a mutant cTnI (Ser43Ala, Ser45Ala) that lacks specific PKC-dependent phosphorylation sites. Treatment of NTG papillary muscles with phenylephrine (PE) resulted in a transient increase and a subsequent 62% reduction in peak twitch force. TG muscles showed no transient increase and only a 45% reduction in force. There was a similar difference in maximum tension between NTG and TG fiber bundles that had been treated with a phorbol ester and had received subsequent detergent extraction. Although levels of cTnI phosphorylation correlated with these differences, the TG fibers also demonstrated a decrease in phosphorylation of cardiac troponin T. The PKC-specific inhibitor chelerythrine inhibited these responses. Our data provide evidence that specific PKC-mediated phosphorylation of Ser43 and Ser45 of cTnI plays an important role in regulating force development in the intact myocardium.

scholarly journals Alterations in Hyper-Variable N-Terminal Region of Cardiac Troponin T Result in Diminished Cardiac Myofilament Function

2012 ◽  
Vol 102 (3) ◽  
pp. 561a
Author(s):  
Sampath K. Gollapudi ◽  
Ranganath Mamidi ◽  
Srilakshmi Mallampalli ◽  
Murali Chandra
Keyword(s):  
Cardiac Troponin ◽  
Troponin T ◽  
Terminal Region ◽  
Cardiac Troponin T ◽  
Myofilament Function ◽  
Cardiac Myofilament

1461-P: Cardiac Troponin T and Troponin I and Incident Diabetes in the General Population: Generation Scotland Scottish Family Health Study

Diabetes ◽  
2019 ◽  
Vol 68 (Supplement 1) ◽  
pp. 1461-P
Author(s):  
PAUL WELSH ◽  
DAVID PREISS ◽  
ARCHIE CAMPBELL ◽  
DAVID J. PORTEOUS ◽  
NICHOLAS L. MILLS ◽  
...  
Keyword(s):  
General Population ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Troponin T ◽  
Family Health ◽  
Incident Diabetes ◽  
Health Study ◽  
Cardiac Troponin T ◽  
Generation Scotland
Sign in / Sign up

Export Citation Format

Share Document