Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of Ca2+, calmodulin, cAMP, the catalytic subunit of cAMP-dependent protein kinase (CSU) and some Ca2+ antagonists were studied in chemically (Triton X-100) skinned coronary smooth muscle. Calmodulin increased the Ca2+ responsiveness of the muscle fiber as indicated by the reduction in the threshold as well as the half-maximal activating Ca2+ concentration. Trifluoroperazine, a calmodulin antagonist, inhibited Ca2+-calmodulin-induced contraction. Both cAMP and CSU were effective inhibitors of contraction induced at an intermediate Ca2+ concentration. Fendiline, a Ca2+-antagonist, at 2 x 10(-4) M produced a significant inhibitory effect, which was reduced by increasing the Ca2+ concentration. From other Ca2+ antagonists tested, W-7, but not D600 and verapamil, produced some inhibitory effect. The data indicate that the response of skinned coronary smooth muscle to Ca2+, calmodulin and cAMP are similar to those obtained with other skinned smooth muscles. Furthermore, skinned fiber preparation can serve as a useful tool to investigate possible direct effects of drugs on the activating and regulatory systems in smooth muscle.
Basic Res Cardiol
PMID:Skinned coronary smooth muscle: calmodulin, calcium antagonists, and cAMP influence contractility. 631 55

The Ca2+ -dependent phosphorylation of proteins has been recognized as a major regulatory mechanism of biological processes. In the heart, protein kinases that are activated by Ca2+ include phosphorylase kinase, myosin light chain kinase, phospholamban kinase [review in 4], and the kinases responsible for phosphorylation of endogenous proteins in the membrane [11] and soluble [6] fractions of the cell. All of these Ca2+-dependent enzymes require the presence, either as an enzyme subunit or as a cofactor, of calmodulin, a Ca2+-binding protein which is involved in various other Ca2+-requiring reactions or processes [review in 3]. We demonstrate here the presence, in the rat heart, of a soluble calmodulin-dependent protein kinase which seems different from those already described in this tissue. The substrate for this enzyme is a 43 kdaltons protein, present in the same soluble fraction.
J Mol Cell Cardiol 1983 Jan
PMID:Phosphorylation of a 43 kdaltons protein from rat heart by a calmodulin-dependent protein kinase. 684 15

Mechanical stress is a major cause of cardiac hypertrophy. Although the mechanisms by which mechanical load induces cardiac cellular hypertrophy have long been a subject of great interest for cardiologists, the lack of a good in vitro system has hampered the understanding of the biochemical mechanisms. For these past several years, however, an in vitro cardiocyte culture system has made it possible to examine the biochemical basis for the signal transduction of mechanical stress. Passive stretch of cardiomyocytes cultured on silicone membranes activates protein kinase cascades of phosphorylation and induces an increase in protein synthesis and the expression of both immediate early genes such as c-fos, c-myc, c-jun, Egr-1, and late response genes such as beta-myosin heavy chain and skeletal alpha-actin. Although an important question regarding how mechanical stimulus is converted into biochemical signals remains unknown, the cultured cardiomyocyte is a good model to examine the signal transduction pathways of mechanical stress.
J Mol Cell Cardiol 1995 Jan
PMID:Molecular mechanism of cardiac cellular hypertrophy by mechanical stress. 776 Mar 38

Vascular tone is regulated by a variety of neurotransmitters, vasoactive hormones and autacoids, and vasoactive drugs. These actions are mediated, at least in part, by actions on the membrane ion channels, exerted either directly or indirectly. In this article, we described evidence that four different protein kinase systems (PK-A, PK-G, PK-C, and Ca2+/CaM-PK) act on and modulate the L-type Ca2+ slow channels in VSM cells and other types of cells. In cardiac muscle, both cAMP/PK-A and cGMP/PK-G have opposing effects. cAMP/PK-A stimulating and cGMP/PK-G inhibiting. In VSM, both cyclic nucleotides and their related kinases act in the same direction, namely both inhibit ICa(L). In skeletal muscle, both cAMP and cGMP also act in the same direction on ICa(L), but to stimulate. Ca2+ channel phosphorylation may be an important mechanism for the cyclic nucleotide-dependent actions of some vasodilators. In cardiac muscle, in addition to the slower indirect pathway--exerted via cAMP/PK-A--there is a faster more-direct pathway for ICa(L) stimulation by the beta-adrenergic receptor. This latter pathway involves direct modulation of the channel activity by the alpha subunit of the Gs-protein (Gs alpha). The two pathways (direct and indirect) are also present in VSM cells, although the indirect pathway produces inhibition of ICa(L)). PK-C and calmodulin-PK also may play roles in regulation of the L-type Ca2+ channels in smooth muscle cells, possibly mediated by phosphorylation of some regulatory-type of protein. Thus, it appears that the L-type Ca2+ slow channel is a complex structure, including perhaps several associated regulatory proteins, which can be regulated by a number of factors intrinsic and extrinsic to the cell (Figs 9, 14).
J Mol Cell Cardiol 1995 Jan
PMID:Regulation of L-type calcium channels of vascular smooth muscle cells. 776 Mar 90

During development of the myocardium the troponin I (TNI) isoform expression is switched from a cAMP-insensitive, slow skeletal muscle TNI to a cAMP-sensitive, cardiac TNI isoform (cTNI). To study the functional consequence of alterations in cTNI expression in the rat heart we investigated the cAMP-controlled cTNI phosphorylation in comparison with alterations of functional properties of isolated cardiac myofibrils during the first postnatal month. cTNI was identified by Western blot analysis followed by a semiquantitative assessment. From the third to the 28th postnatal day the relative concentrations of the cardiac isoform of TNI increased 2.9 +/- 0.3-fold. In the same period the amount of phosphate incorporated into cTNI in the presence of exogenous cAMP-dependent protein kinase (PKA) and 32P[gamma]-ATP was increased 5.8 +/- 0.2-fold (24.2 +/- 3.5 v 140.2 +/- 7.6 pmolP/mg protein loaded onto the gel) whereas the phosphorylation of C-protein was only increased 1.6 +/- 0.2-fold. Ca(2+)-activated isometric tension generation of skinned heart fibres measured in the range of pCa from 6 to 4.5 was not affected by PKA at day 3. However, isometric tension generation of fibres prepared from 28-day-old rats was suppressed by incubation with PKA which was accompanied by a rightward shift in the force/pCa relation. Under these conditions half-maximal tension development was found at pCa 5.38 v 5.52 (p < 0.05) in the absence of PKA. The Ca2+ sensitivity of the contractile apparatus was not affected by PKA-induced phosphorylation of C-protein. These data give direct evidence for the physiological relevance of the onset of cAMP-induced phosphorylation of cTNI for the Ca(2+)-activated tension generation in cardiac myofibrils during postnatal development.
J Mol Cell Cardiol 1994 Sep
PMID:Cardiac troponin I and tension generation of skinned fibres in the developing rat heart. 781 56

Phospholamban is a putative suppressor of the Ca2+ ATPase of the cardiac sarcoplasmic reticulum. The level of mRNA encoding the Ca2+ ATPase has been shown to be increased, whereas the phospholamban mRNA level to be decreased in the ventricles obtained from hyperthyroid rabbits [Nagai R, Zarain-Herzberg A. Brandl CJ, Fujii J. Tada M. MacLennan DH, Alpert NR, Periasamy M. (1989) Proc Natl Acad Sci USA 86: 2966-2970]. The present study was designed to examine whether these effects of thyroid hormone on the expression of the Ca2+ ATPase and phospholamban are exerted directly on cardiac myocytes and whether the resultant incoordinate expression of these proteins alters Ca2+ pumping activity. We studied the levels of phospholamban and Ca2+ ATPase mRNA in primary isolated neonatal rat myocardial cells incubated with triiodothyronine (T3) for 3-48 h and the Ca2+ uptake activity of the microsomes prepared from the cells. Northern blot analysis showed that T3 decreased phospholamban mRNA levels to about a half of control in 24 h. On the other hand, Ca2+ ATPase mRNA gradually increased with time. EC50 for phospholamban mRNA expression was 2.5 x 10(-10) M which was approximately 10 times higher than that for the Ca2+ ATPase. T3 increased Vmax of Ca2+ uptake with the significant reduction of K0.5 for Ca2+ (0.40 +/- 0.02 microM for control v 0.31 +/- 0.02 microM for T3-treated vesicles), indicating that thyroid hormone stimulates Ca2+ pumping activity not only by increasing the Ca2+ ATPase but also decreasing phospholamban. These results suggested that phospholamban regulates the Ca2+ ATPase in dual modes; in short time range, by decreasing the affinity of the Ca2+ ATPase for Ca2+ by phosphorylation of phospholamban with cAMP-dependent protein kinase, and in long time range, by changing the molecular ratio between the two proteins through the regulation of gene expression.
J Mol Cell Cardiol 1994 Sep
PMID:Thyroid hormone enhances Ca2+ pumping activity of the cardiac sarcoplasmic reticulum by increasing Ca2+ ATPase and decreasing phospholamban expression. 781 58

Conventional inhibitors of cyclic AMP-dependent protein kinase lack membrane-permeability or selectivity, or both. The Rp diastereomer of adenosine cyclic 3',5'-phosphorothioate, Rp-cAMPS, is a novel membrane-permeable antagonist of cyclic AMP. We have assessed the ability of this compound to distinguish between cyclic AMP-dependent and cyclic AMP-independent contractile responses elicited in ventricular cardiomyocytes isolated from the hearts of adult rats. Cardiomyocytes were stimulated to contract at 0.5 Hz in the presence of calcium ion (2 mM) and adenosine deaminase (5 units/ml). Contractile shortening was expressed as maximum shortening relative to prestimulus cell length (delta L%). In the presence of a maximally-effective concentration of isoprenaline (100 nM), which acts by a cyclic AMP-dependent mechanism, Rp-cAMPS inhibited the contractile response in a concentration-dependent and time-dependent manner. Following preincubation for 30 min with Rp-cAMPS (100 microM), the contractile response to isoprenaline (100 nM) was 14% of that elicited in the absence of this inhibitor. An incubation time of 30 min was chosen for all subsequent studies. Rp-cAMPS (< or = 200 microM) inhibited the contractile response to isoprenaline (100 nM) significantly and in a concentration-dependent manner, but failed to inhibit the contractile responses elicited by phenylephrine (2 microM) and calcium ion (7 mM) which act by cyclic AMP-independent mechanisms. In the presence of Rp-cAMPs (200 microM), the contractile response to isoprenaline (100 nM) was 24% of that in the absence of inhibitor. Rp-cAMPS was used subsequently to investigate the contractile-coupling mechanisms associated with some novel inotropic agents. Rp-cAMPS (< or = 200 microM) also inhibited the contractile responses to secretin (20 nM) and VIP (20 nM) significantly. In the presence of Rp-cAMPS (200 microM), the contractile response elicited by secretin (20 nM) was 19% of that in the absence of inhibitor, while that elicited by VIP (20 nM) was abolished completely. Rp-cAMPS (< or = 200 microM) failed to inhibit the contractile response elicited by CGRP (1 nM). In summary, Rp-cAMPS is a membrane-permeable, selective antagonist of cyclic AMP in ventricular cardiomyocytes and can be used, in conjunction with the bioassay of the intracellular accumulation of cyclic AMP, to distinguish between cyclic AMP-dependent and cyclic AMP-independent contractile coupling mechanisms in these cells.(ABSTRACT TRUNCATED AT 400 WORDS)
J Mol Cell Cardiol 1994 Nov
PMID:Use of the cyclic AMP antagonist, Rp-cAMPS, to distinguish between cyclic AMP-dependent and cyclic AMP-independent contractile responses in rat ventricular cardiomyocytes. 789 68

Three groups of rats were fed semi-purified diets. Diet I was deficient in essential fatty acids (EFAD), diet II was marginally deficient in essential fatty acids (MEFAD), and diet III contained adequate levels of essential fatty acids (control). After 9 weeks, some rats within each group were killed and cardiac membranes were prepared. Adenylate cyclase activity, [3H]forskolin binding sites, the levels of G proteins (Gi and Gs) and fatty acid composition of the membrane phospholipids were measured. Typical changes of EFA deficiency were observed in fatty acid composition of the membrane phospholipids. Adenylate cyclase activity was significantly lower in membranes of EFA-deficient rats than those of the controls. The MEFAD group gave intermediate values. Similar results were obtained with forskolin-stimulated activity with different concentrations of forskolin. Concentrations of the forskolin binding sites were also lower in the EFAD, but not in the MEFAD rats compared with the controls. There was no significant difference in forskolin binding affinities among the three groups. The decrease in adenylate cyclase activity in EFA-deficient rat heart was partially restored by feeding the control diet for 5 weeks to the EFAD or the MEFAD rats. The levels of Gi alpha and Gs alpha were not significantly different in cardiac membranes of rats fed the EFAD or the MEFAD diets from those of the control group. Lower adenylate cyclase activity in hearts of EFAD rats was also reflected in correspondingly lower activity of cAMP-dependent protein kinase. The results suggest an impairment of the cellular signalling pathway for the production of cAMP in rat heart during EFA deficiency. The beta-adrenergic response of isolated heart preparations obtained from rats fed the three diets was, however, not significantly altered.
J Mol Cell Cardiol 1995 Aug
PMID:Effect of essential fatty acid deficiency on forskolin binding sites, adenylate cyclase and cyclic AMP-dependent protein kinase activity, the levels of G proteins and ventricular function in rat heart. 852 22

Calcium tolerant rabbit cardiomyocytes, isolated by collagenase perfusion, were preincubated for varying periods of time followed by resuspension in fresh media and centrifugation into an ischaemic pellet with restricted extracellular fluid. Pellets were incubated for 240 min under oil at 37 degrees C to mimic severe ischaemia. Time to onset of ischaemic contracture (rod to square transformation) and trypan blue permeability following resuspension in 85 mOSM media were monitored at sequential times. The protocol of Series 1 was a 5-10 min pre-incubation, immediately followed by ischaemic pelleting. Preincubation with pinacidil (50 microM) protected cells from ischaemic insult, but pinacidil added only into the ischaemic pellet did not protect. Protection was abolished by the protein kinase (PKC) inhibitors chelerythrine (10 microM) added with pinacidil and calphostin C (200nM) added only into the ischaemic pellet. Neither PKC inhibitor had an effect on injury of untreated ischaemic myocytes (data not shown). Series 2-5 were preconditioning protocols with a 10 min intervention period, followed by a 30 min oxygenated drug-free period, prior to ischaemic pelleting. In series 2 pinacidil protected cells from ischaemic insult and this protection was abolished when glyburide (10 microM) was present during preincubation, or during post-incubation and ischaemia. Glyburide only partially inhibited the protection when glyburide was added only into the ischaemic pellet. In Series 3, 8-sulfophenyltheophyline (SPT)(100 microM) or adenosine deaminase during preincubation, or SPT only added into the ischaemic pellet abolished pinacidil's protection. In Series 4, cardiomyocytes were ischaemically preconditioned by pelleting for 10 min followed by 30 min reoxygenation. Glyburide during initial ischaemic blocked protection, but when added during post incubation and into the final pellet protection was not reduced. In Series 5 8-cyclopentyl-1,3,dipropylxanthine (DPCPX) (10 microM) added into the final pellet abolished protection by pinacidil, but not protection following ischaemic preconditioning. In contrast to pinacidil, ischaemically preconditioned cells maintain protection in the presence of glyburide, indicating that: (1) pinacidil does not exactly mimic preconditioning and (2) ischaemically preconditioned cells do not require opened K+ATP channels for protection, although they appear to be important during initiation of the preconditioned state. It is hypothesized that pinacidil opening of K+ channels may facilitate induction of preconditioning.
J Mol Cell Cardiol 1995 Aug
PMID:Potassium channels and preconditioning of isolated rabbit cardiomyocytes: effects of glyburide and pinacidil. 852 37

The aim of the present study was to examine the effects of calcitonin gene-related peptide (CGRP) on the K+ channels of vascular smooth muscle cells. Cultured smooth muscle cells from a porcine coronary artery were studied using the patch-clamp technique. Extracellular application of 100 nM CGRP activated two types of K+ channels, the Ca(2+)-activated K+ channel (KCa channel) and the ATP-sensitive K+ channel (KATP channel) in cell-attached patch configurations. In cells pretreated with Rp-cAMPS, a membrane-permeable inhibitor of cAMP-dependent protein kinase (PKA), extracellular application of 100 nM CGRP could not activate the KCa or KATP channel, indicating that the activation of the K+ channels by CGRP occurs in connection with PKA. In the cell-attached patch configurations, extracellular application of 1 mM dibutyryl cAMP, a membrane permeable cAMP, activated KCa and KATP channels. In inside-out patch configurations, application of PKA to the cytosolic side activated both the KCa and KATP channels. These results indicate that CGRP modulates the K+ channels of vascular smooth muscle cells via adenylate cyclase, i.e., cAMP-PKA pathway, and contributes to control of vascular tone.
Basic Res Cardiol
PMID:Calcitonin gene-related peptide activates the K+ channels of vascular smooth muscle cells via adenylate cyclase. 853 58


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