scholarly journals Staurosporine Inhibits Frequency-Dependent Myofilament Desensitization in Intact Rabbit Cardiac Trabeculae

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Kenneth D. Varian ◽  
Brandon J. Biesiadecki ◽  
Mark T. Ziolo ◽  
Jonathan P. Davis ◽  
Paul M. L. Janssen
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Troponin I ◽  
Calcium Transient ◽  
Calcium Sensitivity ◽  
Serine Threonine Kinase ◽  
Frequency Dependent ◽  
Threonine Kinase ◽  
Myosin Light Chain 2 ◽  
Myofilament Calcium Sensitivity

Myofilament calcium sensitivity decreases with frequency in intact healthy rabbit trabeculae and associates with Troponin I and Myosin light chain-2 phosphorylation. We here tested whether serine-threonine kinase activity is primarily responsible for this frequency-dependent modulations of myofilament calcium sensitivity. Right ventricular trabeculae were isolated from New Zealand White rabbit hearts and iontophoretically loaded with bis-fura-2. Twitch force-calcium relationships and steady state force-calcium relationships were measured at frequencies of 1 and 4 Hz at 37 °C. Staurosporine (100 nM), a nonspecific serine-threonine kinase inhibitor, or vehicle (DMSO) was included in the superfusion solution before and during the contractures. Staurosporine had no frequency-dependent effect on force development, kinetics, calcium transient amplitude, or rate of calcium transient decline. The shift in the pCa50of the force-calcium relationship was significant from6.05±0.04at 1 Hz versus5.88±0.06at 4 Hz under control conditions (vehicle,P<0.001) but not in presence of staurosporine (5.89±0.08at 1 Hz versus5.94±0.07at 4 Hz,P=NS). Phosphoprotein analysis (Pro-Q Diamond stain) confirmed that staurosporine significantly blunted the frequency-dependent phosphorylation at Troponin I and Myosin light chain-2. We conclude that frequency-dependent modulation of calcium sensitivity is mediated through a kinase-specific effect involving phosphorylation of myofilament proteins.

Frequency-dependent acceleration of relaxation involves decreased myofilament calcium sensitivity

2007 ◽  
Vol 292 (5) ◽  
pp. H2212-H2219 ◽  
Author(s):  
Kenneth D. Varian ◽  
Paul M. L. Janssen
Keyword(s):  
Intracellular Calcium ◽  
Calcium Concentration ◽  
Troponin I ◽  
Zealand White Rabbit ◽  
Calcium Sensitivity ◽  
Intracellular Calcium Concentration ◽  
Calcium Handling ◽  
Force Frequency ◽  
Frequency Dependent ◽  
Myofilament Calcium Sensitivity

The force-frequency relationship is an intrinsic modulator of cardiac contractility and relaxation. Force of contraction increases with frequency, while simultaneously a frequency-dependent acceleration of relaxation occurs. While frequency dependency of calcium handling and sarcoplasmic reticulum calcium load have been well described, it remains unknown whether frequency-dependent changes in myofilament calcium sensitivity occur. We hypothesized that an increase in heart rate that results in acceleration of relaxation is accompanied by a proportional decrease in myofilament calcium sensitivity. To test our hypothesis, ultrathin right ventricular trabeculae were isolated from New Zealand White rabbit hearts and iontophorically loaded with the calcium indicator bis-fura 2. Twitch and intracellular calcium handling parameters were measured and showed a robust increase in twitch force, acceleration of relaxation, and rise in both diastolic and systolic intracellular calcium concentration with increased frequency. Steady-state force-intracellular calcium concentration relationships were measured at frequencies 1, 2, 3, and 4 Hz at 37°C using potassium-induced contractures. EC50 significantly and gradually increased with frequency, from 475 ± 64 nM at 1 Hz to 1,004 ± 142 nM at 4 Hz ( P < 0.05) and correlated with the corresponding changes in half relaxation time. No significant changes in maximal active force development or in the myofilament cooperativity coefficient were found. Myofilament protein phosphorylation was assessed using Pro-Q Diamond staining on protein gels of trabeculae frozen at either 1 or 4 Hz, revealing troponin I and myosin light chain-2 phosphorylation associated with the myofilament desensitization. We conclude that myofilament calcium sensitivity is substantially and significantly decreased at higher frequencies, playing a prominent role in frequency-dependent acceleration of relaxation.

scholarly journals Imatinib attenuates cerebrovascular injury and phenotypic transformation after intracerebral hemorrhage in rats

2016 ◽  
Vol 311 (6) ◽  
pp. R1093-R1104 ◽  
Author(s):  
William J. Pearce ◽  
Coleen Doan ◽  
Desirelys Carreon ◽  
Dahlim Kim ◽  
Lara M. Durrant ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Intracerebral Hemorrhage ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Cerebral Arteries ◽  
Calcium Sensitivity ◽  
Contractile Protein ◽  
Sprague Dawley ◽  
And Function ◽  
Myofilament Calcium Sensitivity

This study explored the hypothesis that intracerebral hemorrhage (ICH) promotes release of diffusible factors that can significantly influence the structure and function of cerebral arteries remote from the site of injury, through action on platelet-derived growth factor (PDGF) receptors. Four groups of adult male Sprague-Dawley rats were studied ( n = 8 each): 1) sham; 2) sham + 60 mg/kg ip imatinib; 3) ICH (collagenase method); and 4) ICH + 60 mg/kg ip imatinib given 60 min after injury. At 24 h after injury, sham artery passive diameters (+3 mM EGTA) averaged 244 ± 7 µm (at 60 mmHg). ICH significantly increased passive diameters up to 6.4% and decreased compliance up to 42.5%. For both pressure- and potassium-induced contractions, ICH decreased calcium mobilization up to 26.2% and increased myofilament calcium sensitivity up to 48.4%. ICH reduced confocal colocalization of smooth muscle α-actin (αActin) with nonmuscle myosin heavy chain (MHC) and increased its colocalization with smooth muscle MHC, suggesting that ICH promoted contractile differentiation. ICH also enhanced colocalization of myosin light chain kinase (MLCK) with both αActin and regulatory 20-kDa myosin light chain. All effects of ICH on passive diameter, compliance, contractility, and contractile protein colocalization were significantly reduced or absent in arteries from animals treated with imatinib. These findings support the hypothesis that ICH promotes release into the cerebrospinal fluid of vasoactive factors that can diffuse to and promote activation of cerebrovascular PDGF receptors, thereby altering the structure, contractile protein organization, contractility, and smooth muscle phenotype of cerebral arteries remote from the site of hemorrhage.

Propofol Increases Phosphorylation of Troponin I and Myosin Light Chain 2 via  Protein Kinase C Activation in Cardiomyocytes

2003 ◽  
Vol 98 (6) ◽  
pp. 1363-1371 ◽  
Author(s):  
Noriaki Kanaya ◽  
Brad Gable ◽  
Paul A. Murray ◽  
Derek S. Damron
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Light Chain ◽  
Adenosine Triphosphatase ◽  
Myosin Light Chain ◽  
Troponin I ◽  
Adenosine Triphosphatase Activity ◽  
Kinase C ◽  
Myosin Light Chain 2 ◽  
Pkc Alpha

Background Troponin I (TnI) and myosin light chain 2 (MLC2) are important myofibrillar proteins involved in the regulation of myofilament calcium (Ca2+) sensitivity and cardiac inotropy. The objectives of this study were to determine the role of protein kinase C (PKC) in mediating propofol-induced changes in actomyosin adenosine triphosphatase activity in cardiac myofibrils and to examine the extent to which propofol alters the phosphorylation of TnI and MLC2 in cardiomyocytes. Methods Freshly isolated adult rat ventricular myocytes were used for the study. Cardiac myofibrils were extracted for assessment of actomyosin adenosine triphosphatase activity and phosphorylation of TnI and MLC2. Western blot analysis for PKC-alpha was performed on cardiomyocyte subcellular fractions. Simultaneous measurement of intracellular free Ca2+ concentration ([Ca2+](i)) and myocyte shortening was assessed using fura-2 and video edge detection, respectively. Results Propofol (30 microM) reduced the Ca2+ concentration required for activation of actomyosin adenosine triphosphatase activity, and this effect was abolished by bisindolylmaleimide I. In addition, propofol stimulated dose-dependent phosphorylation of TnI and MLC2. PKC activation with phorbol myristic acetate also stimulated an increase in phosphorylation of TnI and MLC2. The actions of propofol and phorbol myristic acetate together on phosphorylation of TnI and MLC2 were not additive. PKC inhibition with bisindolylmaleimide I attenuated phorbol myristic acetate- and propofol-induced phosphorylation of TnI and MLC2. Propofol stimulated translocation of PKC-alpha from cytosolic to membrane fraction. Propofol caused a shift in the extracellular Ca2+-shortening relationship, and this effect was abolished by bisindolylmaleimide I. Conclusions These results suggest that propofol increases myofilament Ca2+ sensitivity via a PKC-dependent pathway involving the phosphorylation of MLC2.

Arachidonic Acid–Dependent Phosphorylation of Troponin I and Myosin Light Chain 2 in Cardiac Myocytes

1995 ◽  
Vol 76 (6) ◽  
pp. 1011-1019 ◽  
Author(s):  
Derek S. Damron ◽  
Ahmad Darvish ◽  
LeeAnn Murphy ◽  
Wendy Sweet ◽  
Christine S. Moravec ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Cardiac Myocytes ◽  
Light Chain ◽  
Myosin Light Chain ◽  
Troponin I ◽  
Myosin Light Chain 2

scholarly journals Chamber specification of atrial myosin light chain-2 expression precedes septation during murine cardiogenesis

1994 ◽  
Vol 269 (24) ◽  
pp. 16961-16970
Author(s):  
S.W. Kubalak ◽  
W.C. Miller-Hance ◽  
T.X. O'Brien ◽  
E. Dyson ◽  
K.R. Chien
Keyword(s):  
Light Chain ◽  
Myosin Light Chain ◽  
Myosin Light Chain 2 ◽  
Atrial Myosin
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