scholarly journals Phosphorylation of the inhibitory subunit of troponin in perfused hearts of mice deficient in phosphorylase kinase. Evidence for the phosphorylation of troponin by adenosine 3′:5′-phosphate-dependent protein kinase in vivo

1977 ◽  
Vol 168 (2) ◽  
pp. 307-310 ◽  
Author(s):  
P J England
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Kinase Activity ◽  
Troponin I ◽  
Protein Kinase Activity ◽  
Phosphorylase Kinase ◽  
Dependent Protein Kinase ◽  
Parallel Increase ◽  
Dependent Protein

When hearts from control and phosphorylase kinase-deficient (I strain) mice were perfused with 0.1 micrometer-DL-isoprenaline, there was a parallel increase in contraction, cyclic AMP concentration and troponin I phosphorylation. However, there was no increase in phosphorylase a in the I-strain hearts, whereas the control hearts showed a large increase. Assays of I-strain heart extracts showed a normal cyclic AMP-dependent protein kinase activity but no phosphorylase kinase activity. It is concluded that troponin I is phosphorylated in intact hearts by protein kinase and not phosphorylase kinase.

scholarly journals Effects of forskolin on contractile responses and protein phosphorylation in the isolated perfused rat heart

1987 ◽  
Vol 246 (3) ◽  
pp. 687-695 ◽  
Author(s):  
P J England ◽  
M Shahid
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Rat Heart ◽  
Kinase Activity ◽  
Troponin I ◽  
Contractile Proteins ◽  
Protein Kinase Activity ◽  
Dependent Protein Kinase ◽  
Perfused Rat Heart ◽  
Dependent Protein

Continuous perfusion of rat hearts with concentrations of forskolin between 0.1 and 12 microM resulted in transient increases in tension after 45 s, followed by a return to the control value after 5 min. In contrast, the content of cyclic AMP increased linearly with time over this period, reaching values up to 35 times control after 5 min. Increases in contractile force, intracellular cyclic AMP concentration and the proportion of phosphorylase in the a form were dependent on the concentration of forskolin when measured 45 s and 120 s after initiation of perfusion. In hearts perfused for 45 s with various concentrations of forskolin, the measured cyclic AMP-dependent protein kinase activity ratio and phosphorylase a content for a given measured intracellular cyclic AMP concentration were both much less than the corresponding values in hearts perfused for 30 s with various concentrations of isoprenaline. The phosphorylation of the contractile proteins troponin-I and C-protein also showed a concentration-dependent increase in hearts perfused with forskolin. There was a strong correlation between the cyclic AMP-dependent protein kinase activity ratios and the phosphorylation of the contractile proteins under all perfusion conditions. These results suggest that cyclic AMP is compartmented in perfused rat heart, and that much of the cyclic AMP produced in response to forskolin is unavailable to activate cyclic AMP-dependent 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.

scholarly journals The role of protein kinase activation in the control of steroidogenesis by adrenocorticotrophic hormone in the adrenal cortex

1973 ◽  
Vol 136 (4) ◽  
pp. 993-998 ◽  
Author(s):  
Malcolm C. Richardson ◽  
Dennis Schulster
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Adrenal Cortex ◽  
Kinase Activity ◽  
Protein Kinase Activity ◽  
Adrenocorticotrophic Hormone ◽  
Dependent Protein Kinase ◽  
Kinase Activation ◽  
Protein Kinase Activation ◽  
Dependent Protein

A method has been developed for investigation of the effect of adrenocorticotrophic hormone (ACTH) on the state of activation of a cyclic AMP-dependent protein kinase within cells of the adrenal cortex. Enzyme activity was measured in terms of the quantity of32P transferred from [γ-32P]ATP to histone under conditions in which bound cyclic AMP did not dissociate from the regulatory subunit of the protein kinase ACTH (1×10-2i.u./ml) caused a rapid and complete activation of the cyclic AMP-dependent protein kinase activity within 2min of hormone addition to the isolated cells. In response to a range of ACTH concentrations a sigmoid log dose–response curve for protein kinase activation was obtained, with half-maximal stimulation attained at about 1×10-3i.u./ml. However, some low doses of ACTH that elicited a marked (but submaximal) steroidogenic response failed to cause a clear stimulation of protein kinase activity in isolated adrenal cells. Theophylline (2mm) potentiated the effect of ACTH on protein kinase activity. The results implicate an important role for protein kinase in ACTH action on the adrenocortical cell.

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