The Muscle-specific Calmodulin-dependent Protein Kinase Assembles with the Glycolytic Enzyme Complex at the Sarcoplasmic Reticulum and Modulates the Activity of Glyceraldehyde-3-phosphate Dehydrogenase in a Ca2+/Calmodulin-dependent Manner

The activity of the SERCA2a Ca2+ pump in the sarcoplasmic reticulum (SR) of cardiac muscle is inhibited by phospholamban. When phospholamban is phosphorylated by cyclic-AMP-dependent protein kinase (PKA) this inhibition is relieved. It is generally agreed that this results in an increase in the Ca2+ sensitivity of the SR Ca2+ pump; however, some investigators have also reported an increase in the maximum velocity of the pump. We have used a sensitive fluorescence method to measure net Ca2+ uptake by native cardiac SR vesicles and compared the effects of a constitutively active subunit of PKA (cPKA) with those of a monoclonal antibody (A1) that binds to phospholamban and is thought to mimic the effect of phosphorylation. Both the Ca2+ sensitivity and the maximum velocity of uptake were increased by cPKA and by A1. The effects of cPKA and A1 on uptake velocity were only slightly additive. No changes in uptake were detected with denatured cPKA or denatured A1. These results indicate that the functional effect of phospholamban phosphorylation is to increase both the Ca2+ sensitivity and the maximum velocity of net Ca2+ uptake into the SR.

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Ca2+ and phospholipid-dependent protein kinase (protein kinase C) activity is not necessarily required for secretion by human neutrophils

Blood ◽

10.1182/blood.v68.4.810.bloodjournal684810 ◽

1986 ◽

Vol 68 (4) ◽

pp. 810-817

Author(s):

KJ Balazovich ◽

JE Smolen ◽

LA Boxer

Keyword(s):

Protein Kinase ◽

Phorbol Esters ◽

Polyacrylamide Gel Electrophoresis ◽

Sodium Dodecyl ◽

Soluble Form ◽

Human Neutrophils ◽

Dependent Manner ◽

Dependent Protein Kinase ◽

Dependent Protein ◽

Dose Dependent

Ca2+-dependent and phospholipid-dependent protein kinase (PKC) is a receptor for and is activated by phorbol esters. This enzyme is reportedly involved in the mechanism of superoxide anion (O2-) production and the release of intracellular granule contents from human neutrophils. As previously reported by others, we found that greater than 75% of the total cellular PKC activity existed in a soluble form in untreated neutrophils and that this activity was enhanced in a dose- dependent manner by phorbol 12-myristate 13-acetate (PMA) and by phorbol 12,13-dibutyrate (PDBu). Furthermore, mezerein, an analogue of PMA that is thought to be a competitive inhibitor, did not activate PKC, and on the contrary, inhibited PMA-stimulated activity in a dose- dependent manner. Pretreatment of intact neutrophils with PMA or PDBu caused the “translocation” of PKC activity to the insoluble cell fraction; PKC translocation was not detected after mezerein stimulation at any of the tested concentrations. Neither did mezerein cause an increase in intracellular Ca2+, as monitored by Quin 2 fluorescence. Both phorbol esters and mezerein stimulated intact neutrophils to generate O2- and release lysosomal enzymes into the extracellular medium. Finally sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis demonstrated key differences in the patterns of endogenous phosphoproteins of neutrophils stimulated with phorbol as compared with mezerein. We therefore suggest that PKC activation may not be the only pathway required to elicit neutrophil responses.

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Differential effects of phospholamban and Ca2+/calmodulin-dependent kinase II on [Ca2+]i transients in cardiac myocytes at physiological stimulation frequencies

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01398.2006 ◽

2008 ◽

Vol 294 (5) ◽

pp. H2352-H2362 ◽

Cited By ~ 9

Author(s):

Andreas A. Werdich ◽

Eduardo A. Lima ◽

Igor Dzhura ◽

Madhu V. Singh ◽

Jingdong Li ◽

...

Keyword(s):

Protein Kinase ◽

Sarcoplasmic Reticulum ◽

Cardiac Myocytes ◽

Wild Type ◽

Dependent Protein Kinase ◽

Frequency Dependent ◽

Physiological Range ◽

Dependent Protein ◽

Isolated Cardiac Myocytes

In cardiac myocytes, the activity of the Ca2+/calmodulin-dependent protein kinase II (CaMKII) is hypothesized to regulate Ca2+ release from and Ca2+ uptake into the sarcoplasmic reticulum via the phosphorylation of the ryanodine receptor 2 and phospholamban (PLN), respectively. We tested the role of CaMKII and PLN on the frequency adaptation of cytosolic Ca2+ concentration ([Ca2+]i) transients in nearly 500 isolated cardiac myocytes from transgenic mice chronically expressing a specific CaMKII inhibitor, interbred into wild-type or PLN null backgrounds under physiologically relevant pacing conditions (frequencies from 0.2 to 10 Hz and at 37°C). When compared with that of mice lacking PLN only, the combined chronic CaMKII inhibition and PLN ablation decreased the maximum Ca2+ release rate by more than 50% at 10 Hz. Although PLN ablation increased the rate of Ca2+ uptake at all frequencies, its combination with CaMKII inhibition did not prevent a frequency-dependent reduction of the amplitude and the duration of the [Ca2+]i transient. High stimulation frequencies in the physiological range diminished the effects of PLN ablation on the decay time constant and on the maximum decay rate of the [Ca2+]i transient, indicating that the PLN-mediated feedback on [Ca2+]i removal is limited by high stimulation frequencies. Taken together, our results suggest that in isolated mouse ventricular cardiac myocytes, the combined chronic CaMKII inhibition and PLN ablation slowed Ca2+ release at physiological frequencies: the frequency-dependent decay of the amplitude and shortening of the [Ca2+]i transient occurs independent of chronic CaMKII inhibition and PLN ablation, and the PLN-mediated regulation of Ca2+ uptake is diminished at higher stimulation frequencies within the physiological range.

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Cellular metabolism regulating H and M currents in bullfrog sympathetic ganglia

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y92-243 ◽

1992 ◽

Vol 70 (S1) ◽

pp. S51-S55 ◽

Cited By ~ 9

Author(s):

Takashi Akasu ◽

Takayuki Tokimasa

Keyword(s):

Protein Kinase ◽

Sympathetic Ganglia ◽

Dependent Manner ◽

Dependent Protein Kinase ◽

Maximal Conductance ◽

Calmodulin Antagonist ◽

M Current ◽

Cationic Current ◽

Voltage Dependent ◽

Dependent Protein

Much evidence has accumulated suggesting that neurons in autonomic and dorsal root ganglia possess voltage-dependent currents that link with transmitter receptors through intracellular signal transduction systems. The M current (IM), a voltage-dependent potassium current, was activated at potentials more positive than −65 mV, while the H current (IH), a voltage-dependent nonselective cationic current, was activated at potentials more negative than −50 mV. The hydrolyzable form of ATP was required to activate IM and IH. Intracellular application of calmodulin enhanced the amplitude of IM in a calcium-dependent manner. IM was reduced by W-7, a calmodulin antagonist, and by ML-9, an inhibitor of calmodulin-dependent protein kinase. IH was enhanced by intracellular loading with cyclic adenosine monophosphate (AMP) or bath application of forskolin and membrane-permeable cyclic AMP analogues. Isobutylmethylxanthine also increased the maximal conductance of IH. IH was depressed by H-8 but not by phorbol ester. It is concluded that the resting membrane conductance of these ganglion cells can be regulated by basal activities of calmodulin-dependent protein kinase and A kinase.Key words: peripheral neurons, M current, H current, calmodulin, adenylate cyclase.

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