scholarly journals AMP-activated Protein Kinase Phosphorylates Cardiac Troponin I at Ser-150 to Increase Myofilament Calcium Sensitivity and Blunt PKA-dependent Function

2012 ◽  
Vol 287 (23) ◽  
pp. 19136-19147 ◽  
Author(s):  
Benjamin R. Nixon ◽  
Ariyoporn Thawornkaiwong ◽  
Janel Jin ◽  
Elizabeth A. Brundage ◽  
Sean C. Little ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Calcium Sensitivity ◽  
Cardiac Troponin I ◽  
Dependent Function ◽  
Amp Activated Protein Kinase ◽  
Myofilament Calcium Sensitivity

Abstract 219: Histidine Substituted Cardiac Troponin I (a164h) Improves Survival And Protects Cardiac Contractility During Acute Hypoxia In The Aged Murine Heart.

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Nathan Palpant ◽  
Sharlene Day ◽  
Kimber Converso ◽  
Joseph Metzger
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Acute Hypoxia ◽  
Cardiac Contractility ◽  
Systolic Pressure ◽  
Calcium Sensitivity ◽  
The Elderly ◽  
Cardiac Troponin I ◽  
Pump Failure ◽  
Myofilament Calcium Sensitivity

Contractile dysfunction associated with ischemia is a significant cause of morbidity and mortality particularly in the elderly. Strategies designed to protect the aged heart from ischemia-mediated pump failure are needed. We have generated transgenic (Tg) mice expressing a modified form of adult cardiac troponin I, the Ca ++ -activated molecular switch of the myofilament. Consonant with the fetal isoform, this transgene encodes a histidine substitution (A164H) in the critical switch domain of TnI thus increasing myofilament calcium sensitivity in a pH-dependent manner. We hypothesized that aged mice (24 months), intrinsically susceptible to myocardial dysfunction, would retain improved cardiac contractility at baseline and during an acute hypoxic challenge by means of myofilament-mediated calcium sensitization. Methods/Results: At baseline, by echocardiography, Tg hearts had increased systolic function, with a 26% higher mean ejection fraction compared to nontransgenic (Ntg) mice: 75 ± 3% [Tg: n = 13] vs. 63 ± 4% [Ntg: n = 12], P < 0.05, with no differences in diastolic function between the groups. To study the effects of acute hypoxia on cardiac hemodynamics mice underwent microconductance Millar catheterization while ventilated with 12% oxygen. Aged Tg mice had improved survival compared to Ntg mice: time to pump failure (65% of baseline peak systolic pressure) 11.59 ± 1.25 min. [Tg: n = 3] vs. 4.11 ± 1.90 min. [Ntg: n = 3], P < 0.05. After four minutes of hypoxia, Tg mice had markedly improved cardiac contractility compared to Ntg mice with increased stroke volume (30.05 ± 4.49 uL [Tg] vs. 13.23 ± 3.21 uL [Ntg], P < 0.05), end systolic pressure (106.09 ± 11.81 mmHg [Tg] vs. 64.49 ± 4.05 mmHg [Ntg], P < 0.05) and rate of positive left ventricular pressure development (12958.66 ± 2544.68 mmHg/sec [Tg] vs. 5717.00 ± 745.67 mmHg/sec [Ntg], P = 0.05). Conclusion: An alteration in myofilament calcium sensitivity via a pH-responsive histidine button in cardiac troponin I augments baseline heart function in Tg mice over their lifetime. During acute hypoxia, cTnI A164H improves survival in aged mice by maintaining cardiac contractility, and thus holds promise for the design of gene therapeutics to treat pump failure associated with acute ischemic events in the elderly.

scholarly journals Increased myofilament calcium sensitivity is associated with decreased cardiac troponin I phosphorylation in the diabetic rat heart

2021 ◽  
Author(s):  
Angela C. Greenman ◽  
Gary M. Diffee ◽  
Amelia S. Power ◽  
Gerard T. Wilkins ◽  
Olivia M. S. Gold ◽  
...  
Keyword(s):  
Cardiac Troponin ◽  
Rat Heart ◽  
Troponin I ◽  
Calcium Sensitivity ◽  
Cardiac Troponin I ◽  
Diabetic Rat ◽  
Myofilament Calcium Sensitivity

Abstract 1478: AMP-Activated Protein Kinase Phosphorylates Cardiac Troponin I and Alters Contractility in Murine Ventricular Myocytes

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
S Marisa Oliveira ◽  
Yin-Hua Zhang ◽  
Joanne Davies ◽  
David Carling ◽  
Barbara Casadei ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Ventricular Myocytes ◽  
Intracellular Localization ◽  
Left Ventricular ◽  
Cardiac Troponin I ◽  
Compound C ◽  
Cardiac Phenotype ◽  
Amp Activated Protein Kinase

In the heart, AMP-activated protein kinase (AMPK) is critical in the regulation of energy balance and in myocardial signaling, and is activated especially during ischaemia and exercise. It is a αβγ heterotrimer, with α being the catalytic subunit. Mutations affecting the regulatory γ2 subunit have been shown to cause a cardiac phenotype of hypertrophy and conduction disease, thus suggesting a specific role for this subunit in the heart. The γ isoforms are highly conserved at their C-termini but very different at their N-termini; hence we have investigated whether the unique N-terminus of γ2 could be involved in conferring substrate specificity or in determining intracellular localization. We have undertaken a GAL4 -based yeast two-hybrid assay to screen a human heart cDNA library using the N-terminal 273 residues of γ2 as bait. Five proteins were identified as true interactors in the yeast assay, one of these being cardiac troponin I (cTnI). In vitro studies showed that cTnI (isolated or reconstituted as troponin complex) is a good substrate for AMPK. Studies using site-specific cTnI mutants and mass spectrometry identified Ser-150 as the principal residue phosphorylated by AMPK. Actomyosin ATPase assays showed that phosphorylation at this residue resulted in increased Ca 2+ sensitivity of contractile regulation (ΔpCa 50 =+0.07). Treatment of cardiomyocytes with the AMPK activator AICAR for 15 min resulted in prolonged relaxation (time to 50% relaxation, TR50) in field stimulated left ventricular myocytes of C57B/6 mice (TR50 in ms: 29.8±1.4 in control and 38.0±2.4 with AICAR, n=11, 3 Hz and 35 o C). There was a tendency towards an increase in contraction with AICAR. Pretreatment of myocytes with AMPK inhibitor compound C (10 μM) abolished the effects of AICAR on myocytes (TR50 in ms: 30.9±1.7 before AICAR and 31.5±2.6 after AICAR, n=9). The effect of AICAR was mediated without altering the amplitude of the Ca 2+ transient, suggesting that it may be caused by a change in myofilament Ca 2+ -sensitivity and consistent with AMPK phosphorylation of cTnI. We hypothesize that cTnI phosphorylation by AMPK may represent a novel mechanism of regulation of cardiac function.

scholarly journals Increased myofilament calcium sensitivity is associated with decreased cardiac troponin I phosphorylation in the diabetic rat heart

2021 ◽  
Author(s):  
Angela Greenman ◽  
Gary M. Diffee ◽  
Amelia Power ◽  
Gerard T. Wilkins ◽  
Olivia M. S. Gold ◽  
...  
Keyword(s):  
Cardiac Troponin ◽  
Troponin I ◽  
Calcium Sensitivity ◽  
Cardiac Troponin I ◽  
Diabetic Heart ◽  
Diabetic Rat ◽  
Zdf Rat ◽  
Regulation Of Contraction ◽  
Systolic And Diastolic Function ◽  
Myofilament Calcium Sensitivity

Abstract Background The diabetic heart has impaired systolic and diastolic function independent of other comorbidities. The availability of calcium is altered, but does not fully explain the cardiac dysfunction seen in the diabetic heart. Thus, we explored if myofilament protein regulation of contraction is altered. Methods Calcium sensitivity (pCa50) was measured in Zucker Diabetic Fatty (ZDF) rat hearts at the initial stage of diabetes (12-week-old) and after 8 weeks of uncontrolled hyperglycaemia (20-week-old) and in non-diabetic (nDM) littermates. Skinned cardiomyocytes were connected to a capacitance-gauge transducer and a torque motor to measure force as a function of pCa (-log[Ca2+]). Fluorescent gel stain (ProQ Diamond) was used to measure total protein phosphorylation. Specific phospho-sites on cardiac troponin I (cTnI) and total cTnI O-GlcNAcylation were quantified using immunoblot. Results pCa50 was greater in both 12- and 20-week-old diabetic (DM) rats compared to nDM littermates (p = 0.0005). Total cTnI and cTnI serine 23/24 phosphorylation were lower in DM rats (p = 0.003 & p = 0.01, respectively), but cTnI O-GlcNAc protein expression was not different. pCa50 is greater in DM rats and corresponds with an overall reduction in cTnI phosphorylation. Conclusions These findings indicate that myofilament calcium sensitivity is increased and cTnI phosphorylation is reduced in ZDF DM rats, which suggests an important role for cTnI phosphorylation in the DM heart.

scholarly journals AMP-Activated Protein Kinase Phosphorylates Cardiac Troponin I and Alters Contractility of Murine Ventricular Myocytes

2012 ◽  
Vol 110 (9) ◽  
pp. 1192-1201 ◽  
Author(s):  
Sandra Marisa Oliveira ◽  
Yin-Hua Zhang ◽  
Raquel Sancho Solis ◽  
Henrik Isackson ◽  
Mohamed Bellahcene ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Ventricular Myocytes ◽  
Cardiac Troponin I ◽  
Amp Activated Protein Kinase

scholarly journals The phosphorylation of troponin I from cardiac muscle

1975 ◽  
Vol 149 (3) ◽  
pp. 525-533 ◽  
Author(s):  
H A Cole ◽  
S V Perry
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Cardiac Muscle ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I ◽  
Phosphorylase Kinase ◽  
Dependent Protein Kinase ◽  
Dependent Protein

1. Troponin I isolated from fresh cardiac muscle by affinity chromatography contains about 1.9 mol of covalently bound phosphate/mol. Similar preparations of white-skeletal-muscle troponin I contain about 0.5 mol of phosphate/mol. 2. A 3':5'-cyclic AMP-dependent protein kinase and a protein phosphatase are associated with troponin isolated from cardiac muscle. 3. Bovine cardiac 3':5'-cyclic AMP-dependent protein kinase catalyses the phosphorylation of cardiac troponin I 30 times faster than white-skeletal-muscle troponin I. 4. Troponin I is the only component of cardiac troponin phosphorylated at a significant rate by the endogenous or a bovine cardiac 3':5'-cyclic AMP-dependent protein kinase. 5. Phosphorylase kinase catalyses the phosphorylation of cardiac troponin I at similar or slightly faster rates than white-skeletal-muscle troponin I. 6. Troponin C inhibits the phosphorylation of cardiac and skeletal troponin I catalysed by phosphorylase kinase and the phosphorylation of white skeletal troponin I catalysed by 3':5'-cyclic AMP-dependent protein kinase; the phosphorylation of cardiac troponin I catalysed by the latter enzyme is not inhibited.

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