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)

Caclium initiates smooth muscle contraction by activating an enzyme, myosin light chain kinase. This enzyme catalyzes the transfer of phosphate from adenosine triphosphate to the 20,000 dalton light chain of myosin. In its phosphorylated form myosin interacts with actin to produce muscle contraction. The mechanism by which calcium activates myosin kinase requires (1) the binding of calcium to a 16,500 dalton calcium-binding protein (calmodulin), and (2) the binding of calmodulin-calcium to a 125,000 dalton catalytic subunit. This two protein complex is the active form of myosin light chain kinase. Smooth muscle relaxation is mediated by cyclic adenosine 3':5' monophosphate (cyclic AMP). One nechanism by which the latter may exert a direct effect on actin-myosin interaction is through the activation of a cyclic AMP-dependent protein kinase that can phosphorylate the 125,000 dalton component of myosin light chain kinase. Phosphorylation of myosin light chain kinase decreases the activity of the enzyme, thus favoring the unphosphorylated form of myosin, which cannot interact with actin to produce smooth muscle contraction.
Am J Cardiol 1979 Oct 22
PMID:Role of calcium and cyclic adenosine 3':5' monophosphate in regulating smooth muscle contraction. Mechanisms of excitation-contraction coupling in smooth muscle. 22 62

The protein kinase activity in cytosol was similar in control, ischemic, and reperfused hearts; however, a 1.5-fold increase in membrane protein kinase activity was induced by ischemia and reperfusion. The H-7 inhibitable cytosolic protein kinase activity decreased by 40% with 30 min ischemia, while that of membrane fraction increased 1.8-fold. However, the CGS9343B inhibitable protein kinase activity in cytosolic fractions was unaffected by ischemia, while that of membrane increased by about 1.7-fold. These results suggest that myocardial ischemia is associated with enhanced protein kinase C and calmodulin-dependent kinase activities in membrane fraction. Furthermore, the results also suggest a translocation of protein kinase C activity from the cytosol to the membrane. Reperfusion of ischemic myocardium did not result in any further increase of protein kinase C and calmodulin-dependent kinase activities in the membrane. These enhanced protein kinase activities also resulted in an enhanced phosphorylation of endogenous membrane proteins. The creatine kinase released from the heart was increased by both ischemia and reperfusion. Therefore, these results suggest that biochemical cascades of reactions caused by enhanced membrane protein kinase C and calmodulin-dependent kinase activities may contribute to ischemic-reperfusion injury.
Basic Res Cardiol
PMID:Enhanced membrane protein kinase C activity in myocardial ischemia. 131 57

The aim of the present study was to further elucidate the physiological role of the calcium-calmodulin (Ca(2+)-Cm)-dependent protein kinase system on phospholamban phosphorylation in the intact functioning heart. The effect of increasing extracellular calcium concentration [Ca]o on phospholamban phosphorylation (PHPL) was studied under different experimental conditions: (a) regular twitches and ryanodine induced-tetani both in the presence and in the absence of 3 x 10(-8) M isoproterenol and (b) Post-stimulation potentiation (PSP), i.e. the potentiation of contractility that follows a period of rapid repetitive stimulation. In the regular twitch, the increase in [Ca]o enhanced contractility both, in the absence and in the presence of beta-stimulation without changing basal or isoproterenol stimulated cAMP levels respectively. This increase in contractility was accompanied by a significant enhancement of PHPL-from 90.6 +/- 16.4 to 216 +/- 35.2 pmols 32Pi/mg protein at 0.25 and 3.85 mM [Ca]o respectively-only when isoproterenol was present. The calmodulin antagonist W-7 significantly decreased the isoproterenol-induced phosphorylation of phospholamban at [Ca]o 1.35 mM. Similar results were obtained under tetanic conditions. When myocardial contractility was enhanced by PSP up to ten-times with respect to the regular twitch, no detectable effect in PHPL was observed. Indirect evidence obtained from skinned rat cardiac trabeculae suggested that the failure of the cAMP-independent mechanisms to phosphorylate phospholamban is not related to a deficient increase in intracellular calcium. The results support the notion that the increase in intracellular calcium induces an increase in PHPL only at high intracellular cAMP levels.
J Mol Cell Cardiol 1992 Apr
PMID:Phosphorylation of phospholamban in the intact heart. A study on the physiological role of the Ca(2+)-calmodulin-dependent protein kinase system. 132 Jan 29

It is unclear whether reported fluctuations in the level of adenosine 3',5'-cyclic monophosphate (cAMP) during a single cardiac cycle in ventricular muscle are associated with distal changes in cAMP-dependent processes. The degree of cAMP variation and its effect, if any, on biochemical sequelae during the cardiac cycle, were investigated by determining the level of cAMP and the activity ratios of cAMP-dependent protein kinase and glycogen phosphorylase in the rat ventricular myocardium. Isolated perfused hearts contracting at 240 beats/min and free of exogenously administered catecholamines were freeze-clamped, utilizing an automated clamping device capable of freezing the entire heart in less than 50 ms. The cardiac cycle was segmented into phases utilizing three different segmentation schemes. No significant difference was detected between phases regardless of the method of segmentation for cAMP, cAMP-dependent protein kinase, or glycogen phosphorylase levels. These results suggest that the levels of cAMP and the activities of cAMP-dependent protein kinase and glycogen phosphorylase do not vary significantly during a single cardiac cycle in the mammalian myocardium.
J Mol Cell Cardiol 1992 May
PMID:Lack of oscillations in cyclic AMP, cAMP-protein kinase and glycogen phosphorylase during the cardiac cycle in perfused rat hearts. 132 13

Calcium transport by the cardiac sarcoplasmic reticulum is depressed in human dilated cardiomyopathy, but the mechanisms involved are not clear. The possible involvement of immunological mechanisms was explored by evaluating the effect of sera from 49 patients with dilated cardiomyopathy on oxalate-facilitated Ca2+ uptake. In 14 of these patients, serum or IgG induced a time- and concentration-dependent decline (29 +/- 4% at 100-fold serum dilution) in Ca2+ transport. In 14 patients, autoantibodies against the beta 1-adrenoceptor were also demonstrated by a ligand binding inhibition assay. Serum from these patients inhibited the isoproterenol-mediated stimulation of Ca2+ uptake in permeabilized cardiac myocytes, but did not prevent the effect of protein kinase A. Anti-beta-receptor antibodies were present in 50% of the sera inhibiting Ca2+ uptake compared to 20% of those without inhibitory activity, (p less than 0.01). There was a strong correlation between the inhibition of sarcoplasmic reticulum Ca2+ transport and the HLA-DR4 phenotype (78% compared to 30% in patients with no inhibitory effect). These results suggest that immunological mechanisms play an important role in modifying sarcoplasmic reticulum function in about a third of the patients with detailed cardiomyopathy.
Basic Res Cardiol 1992
PMID:Immune-mediated modulation of sarcoplasmic reticulum function in human dilated cardiomyopathy. 132 63

Cardiac gap junctions permit the conduction and propagation of the electrical impulses that are responsible for the synchronous contraction of the myocardium (Page and Manjunath, 1986). Cardiac gap junctions are formed by the association of connexin molecules within the plasma membrane of heart cells. They create aqueous channels that permit exchange of ions and other small molecules between adjacent cells. Intercellular communication via these channels may be regulated by phosphorylation. cAMP was shown to increase junctional conductance and stimulate phosphorylation of connexin32 in cultures of dissociated liver hepatocytes (Saez et al., 1986). Furthermore, a 47 kDa protein purified from dog heart gap junctions was phosphorylated in vitro by the catalytic subunit of protein kinase A (Pressler and Hathaway, 1987). Other studies have demonstrated that cAMP enhanced junctional conductance in intact heart and isolated heart cells (De Mello, 1986; De Mello and van Loon, 1987; Burt and Spray, 1988). This report provides direct evidence that the heart gap junction protein, connexin43, from unstimulated heart tissues and cultured myocytes is phosphorylated stoichiometrically in vivo. Phosphorylation of 45 and 47 kDa connexin43-related proteins occurred predominantly on serine. In addition, the 47 kDa protein contained a low-level of phosphothreonine.
J Mol Cell Cardiol 1991 Jun
PMID:Evidence that heart connexin43 is a phosphoprotein. 165 41

Adenosinergic and muscarinic agents have been shown to attenuate the catecholamine-induced augmentation of both protein phosphorylation and contractile state in perfused hearts. The attenuation by phenylisopropyl-adenosine (PIA) and carbamylcholine chloride (CARB) of the isoproterenol (ISO)-induced incorporation of 32P into protein substrates was examined in isolated rat ventricular myocytes. 32P-labelled myocytes exposed to ISO (0.1 microM, 30 s) demonstrated up to an eight-fold increase of 32P incorporation into three protein substrates (155, 31, 6 kD). When myocytes were pre-incubated with either PIA or CARB for 60 s, the ISO-induced 32P incorporation in the 31 kD and the 155 kD substrates was attenuated 37% and 25%, respectively by 1 microM PIA and only 23% and 11%, by 10 microM PIA. A concentration of 1 microM CARB produced a 24% and 17% reduction in these same substrates while 10 microM CARB produced a 44% and 50% reduction. The effects of ISO were antagonized by 10 microM propanolol. The inhibitory effects of PIA were antagonized by the theophylline, sulfophenyltheophylline and dipropylcyclopentylxanthine, whereas atropine antagonized the inhibitory effects of CARB. The 32P incorporation elicited by 1 microM forskolin was reduced more by CARB than PIA. Additionally, while PIA and CARB reduced the ISO-induced increase in cAMP-dependent protein kinase (PKA) activity by 48% and 41% respectively, only CARB attenuated the ISO-elicited increase in cAMP levels, attenuating this response by 58%. The results indicate that PIA was less effective in attenuating ISO-induced 32P incorporation at higher concentrations than at lower concentrations. Moreover, this compound was less potent than CARB at attenuating the effects of ISO. It is conceivable that this difference could be related to activation of stimulatory adenosine receptors (A2) and/or a greater density of muscarinic receptors including multiple inhibitory muscarinic pathways.
J Mol Cell Cardiol 1991 Jun
PMID:Adenosine and acetylcholine reduce isoproterenol-induced protein phosphorylation of rat myocytes. 165 44

Early studies in whole heart indicated that cGMP antagonized the positive inotropic effects of catecholamines and cAMP. However, the regulation of cGMP levels by a variety of agents was not always consistent with their effects on contractility. It is now clear that at least two major cell types in whole heart, cardiac myocytes and vascular smooth muscle cells, differ markedly in their mechanisms of cGMP regulation and response to cGMP. Furthermore, experiments on isolated cardiac myocytes indicate that the mechanism of cGMP action even in this single cell type can be multifaceted. Cyclic GMP inhibits the L-type calcium channel current (ICa), which is the major source of Ca++ entry into heart cells, and which plays a predominant role in the initiation and regulation of cardiac electrical and contractile activities. Patch-clamp measurements of ICa indicate that in isolated frog myocytes cGMP inhibits ICa by stimulation of cAMP phosphodiesterase (cGS-PDE), whereas in purified rat ventricular myocytes, cGMP predominantly inhibits ICa via a mechanism involving cGMP-dependent protein kinase (cGMP-PK). Under certain conditions, cGMP can also inhibit a cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) and thereby produce a stimulatory effect on ICa. Biochemical characterization of the endogenous PDEs and cGMP-PK in purified cardiac myocytes provided further evidence in support of these mechanisms of cGMP action on ICa.
Basic Res Cardiol
PMID:Signal transduction by cGMP in heart. 166 25

A monoclonal antibody against phospholamban has been reported to increase Ca2+ uptake by cardiac sarcoplasmic reticulum. We compared the effect of this antibody on Ca2+ pump ATPase activity of cardiac sarcoplasmic reticulum vesicles to the effect of cAMP-dependent phosphorylation of phospholamban. The antibody markedly stimulated the Ca(2+)-dependent ATPase activity in parallel to the increase in Ca2+ uptake by cardiac sarcoplasmic reticulum. When the Ca(2+)-dependent profile of the ATPase activity was compared, the KCa was shifted from 1.24 to 0.62 microM by the antibody, whereas cAMP-dependent phosphorylation of phospholamban shifted the KCa to 0.84 microM. When cardiac sarcoplasmic reticulum vesicles were treated with both cAMP-dependent protein kinase and the antibody, the stimulation was the same as that with the antibody alone. Thus, the Ca2+ pump ATPase seems to be fully activated by the antibody. The stoichiometry between Ca2+ uptake and ATPase rate was around 1 and no significant change was observed by the treatment with the antibody. Therefore, the stimulation of Ca2+ uptake of cardiac sarcoplasmic reticulum by the antibody occurred by the stimulation of Ca2+ pump ATPase, not by other mechanisms such as channel activity of phospholamban. These results indicate that the binding of the antibody to phospholamban produces essentially the same mode of action on Ca2+ pump ATPase as that of phospholamban phosphorylation. The antibody and phospholamban phosphorylation appear to release the inhibitory action of phospholamban on Ca2+ pump ATPase, resulting in the stimulation of Ca2+ pump.
J Mol Cell Cardiol 1991 Nov
PMID:Effects of monoclonal antibody against phospholamban on calcium pump ATPase of cardiac sarcoplasmic reticulum. 166 13

The influence of the catalytic subunit (20 micrograms/ml) of cAMP-dependent protein kinase on junctional conductance (gj) of isolated rat ventricular cell pairs was investigated. It was found that gj was increased by 90% within 4 to 5 min when the subunit was dialysed into both cells. The dialysis of the catalytic subunit into just one cell of the pair increased gj and generated rectification of junctional membrane. The regulatory subunit (20 micrograms/ml) of cAMP-dependent protein kinase reduced gj by about 17% when dialysed into both cells of pairs. These results might indicate that the symmetric phosphorylation of junctional proteins in the two hemichannels increases gj without rectification while asymmetric phosphorylation generates rectification of junctional membrane.
J Mol Cell Cardiol 1991 Mar
PMID:Further studies on the influence of cAMP-dependent protein kinase on junctional conductance in isolated heart cell pairs. 188 Aug 18


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