Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phospholamban inhibits the Ca(2+)-ATPase of cardiac sarcoplasmic reticulum by lowering its affinity for Ca2+. In earlier studies (Toyofuku, T., Kazimierz, K., Tada, M., and MacLennan, D. H. (1993) J. Biol. Chem. 268, 2809-2815), parts of the phosphorylation and nucleotide binding/hinge domains of the Ca(2+)-ATPase were shown to be essential for phospholamban interaction. In order to identify the sites in phospholamban which interact with the Ca(2+)-ATPase, a series of mutants containing amino acid replacements in the cytoplasmic and transmembrane regions of phospholamban were co-expressed with the cardiac/slow-twitch muscle Ca(2+)-ATPase isozyme, SERCA2a, in HEK-293 cells. Mutation of residues in the cytoplasmic 1A domain of phospholamban, including positively charged residues, Lys3, Arg9, Arg13, and Arg14, negatively charged residue, Glu2, hydrophobic residues, Val4, Leu7, Ala11, Ile12, Ala15, and Ile18, and phosphorylation site residues, Ser16 and Thr17, resulted in loss of the inhibitory effect of phospholamban on Ca2+ transport by the Ca(2+)-ATPase. By contrast, mutation of Met1, Gln5, Tyr6, Thr8, Ser10, Glu19, or Met20 or of residues in the cytoplasmic 1B domain (Pro21 to Asn30) and of Cys41 in the transmembrane domain (Leu31 to Leu52) did not diminish the inhibitory effects of phospholamban on Ca2+ transport. These results suggest that a region essential for functional association of phospholamban with the Ca(2+)-ATPase lies in the cytoplasmic 1A domain of phospholamban.
...
PMID:Amino acids Glu2 to Ile18 in the cytoplasmic domain of phospholamban are essential for functional association with the Ca(2+)-ATPase of sarcoplasmic reticulum. 790 83

The Ca-ATPase in the cardiac sarcoplasmic reticulum membrane is regulated by an amphipathic transmembrane protein, phospholamban. We have used time-resolved phosphorescence anisotropy to detect the microsecond rotational dynamics, and thereby the self-association, of the Ca-ATPase as a function of phospholamban phosphorylation and physiologically relevant calcium levels. The phosphorylation of phospholamban increases the rotational mobility of the Ca-ATPase in the sarcoplasmic reticulum bilayer, due to a decrease in large-scale protein association, with a [Ca2+] dependence parallel to that of enzyme activation. These results support a model in which phospholamban phosphorylation or calcium free the enzyme from a kinetically unfavorable associated state.
...
PMID:The physical mechanism of calcium pump regulation in the heart. 791 99

Selective and specific changes in gene expression characterize the end-stage failing heart. However, the pattern and relation of these changes to evolving systolic and diastolic dysfunction during development of heart failure remains undefined. In the present study, we assessed steady-state levels of mRNAs encoding a group of cardiac proteins during the early development of left ventricular dysfunction in dogs with pacing-induced cardiomyopathy. Corresponding hemodynamic assessments were made in the conscious state in the same animals and at the same time points at baseline, after 1 week of ventricular pacing, and at the onset of clinical heart failure. Systolic dysfunction dominated after 1 week of pacing, whereas diastolic dysfunction was far more pronounced with the onset of heart failure. Atrial natriuretic factor mRNA was undetectable in 7 of 12 hearts at baseline but was expressed in all hearts at 1 week (P < .01 by chi 2 test), and it increased markedly with progression to failure (P = .05). Creatine kinase-B mRNA also rose markedly with heart failure (P < .01). Levels of mRNA encoding beta-myosin heavy chain, mitochondrial creatine kinase, phospholamban, and sarcoplasmic reticulum Ca(2+)-ATPase did not significantly change from baseline, despite development of heart failure. Additional analysis to determine if these mRNA changes were related to the severity of diastolic or systolic dysfunction revealed that phospholamban mRNA decreased in hearts with larger net increases in end-diastolic pressure (+19.2 +/- 1.9 mm Hg) compared with those hearts in which it did not change (+4.0 +/- 4.9, P < .02).(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Endomyocardial gene expression during development of pacing tachycardia-induced heart failure in the dog. 792 7

Effects of KN-62 (1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4- phenylpiperazine), a specific Ca++/calmodulin (CaM)-dependent protein kinase inhibitor, were examined on the rate of spontaneous beating and the intracellular Ca++ transient of cultured myocytes from fetal mouse ventricle. KN-62 depressed the rate of beating in a dose-dependent fashion. Spontaneous beating ceased 10 min after the administration of 1 microM KN-62 and recovered gradually after washing with cultured medium. Addition of KN-04 [N-(1-1[P-(5-isoquinolinsulfonyl)benzyl]-2-(4- phenylpiperazinyl)ethyl)-5-isoquinolinsulfonamide; 1 microM], an analog of KN-62, did not change the rate of beating. In the experiment using an intracellular Ca++ fluorescence indicator, fluo-3, KN-62 depressed the fluo-3 intensity at a systolic phase. The kinase activity to syntide-2 of Ca++/CaM kinase II purified from the rabbit heart was inhibited by KN-62, but not by KN-04. Addition of KN-62 inhibited the phosphorylation of phospholamban by Ca++/CaM kinase II in a dose-dependent manner. KN-62 depressed the Ca(++)-pumping ATPase activity in the presence of Ca++ and CaM by 32%. These findings indicate that Ca++/CaM kinase II changes an intracellular Ca++ transient and modulates the rate of beating at least in part.
...
PMID:KN-62, a specific Ca++/calmodulin-dependent protein kinase inhibitor, reversibly depresses the rate of beating of cultured fetal mouse cardiac myocytes. 793 85

The peptide MEKVQYLTRSAIRRASTIEMPQQAR-Cys corresponding to residues 1-25 of phospholamban was found to inhibit the ATPase activity of skeletal muscle Ca(2+)-ATPase, but to have no effect on the Ca(2+)-dependence of its activity. The peptide was found to decrease the rate of the Ca2+ transport step (E1PCa2-->E2P) by a factor of 2.4. The rate of this same step was decreased by poly(L-Arg) by a factor of 2.2. The peptide shifted the E2-E1 equilibrium of the ATPase towards E1 by a factor of 4 due to stronger binding to the E1 than to the E2 conformation of the ATPase; dissociation constants for binding to E1 and E2 were estimated as 3 and 10 microM respectively. The peptide had no effect on the level of phosphorylation by Pi in the absence of Ca2+ or on the rate of phosphorylation by ATP in the presence of Ca2+.
...
PMID:The hydrophilic domain of phospholamban inhibits the Ca2+ transport step of the Ca(2+)-ATPase. 798 Apr 11

We have demonstrated recently that in cardiac sarcoplasmic reticulum (SR), a membrane-associated Ca2+/calmodulin-dependent protein kinase (CaM kinase) phosphorylates and activates the Ca(2+)-pumping ATPase (Ca(2+)-ATPase) in addition to phosphorylating the previously characterized substrates, phospholamban, and Ca2+ release channel (ryanodine receptor) (Xu, A., Hawkins, C., and Narayanan, N. (1993) J. Biol. Chem. 268, 8394-8397). The present study shows that a CaM kinase regulatory system capable of modulating SR Ca2+ pump activity through direct phosphorylation of the Ca(2+)-ATPase is functional in slow twitch but not fast twitch skeletal muscle. Incubation of SR vesicles isolated from rabbit slow twitch (soleus) and fast twitch (adductor magnus) skeletal muscles in the presence of Ca2+ and calmodulin resulted in phosphorylation of the Ca(2+)-ATPase in slow twitch muscle SR but not in fast twitch muscle SR. Exogenous CaM kinase II, which stimulated phosphorylation of the cardiac and slow twitch muscle SR Ca(2+)-ATPase, failed to phosphorylate fast twitch muscle SR Ca(2+)-ATPase. These observations demonstrate that CaM kinase-catalyzed phosphorylation of the Ca2+ pump is isoform-specific since heart and slow twitch muscle express the same Ca(2+)-ATPase isoform (SERCA2a), which is distinct from that of fast twitch muscle (SERCA1). As in the case of cardiac SR Ca(2+)-ATPase, phosphorylation of the slow twitch muscle SR Ca(2+)-ATPase (occurring at a serine residue) resulted in a 2-fold increase in catalytic activity of the enzyme without alteration in its Ca2+ sensitivity. In addition, Ca2+/calmodulin-dependent prephosphorylation of slow twitch muscle SR resulted in a greater than 2-fold increase in its Ca2+ transport activity. In both cardiac and slow twitch muscle SR, phosphorylation of the Ca(2+)-ATPase by the endogenous CaM kinase occurred rapidly (maximum within 2 min at 37 degrees C), had similar pH optimum (8.5-9.0), temperature optimum (30 degrees C), and calmodulin concentration-dependence (k0.5 50-60 nM). cAMP-dependent protein kinase did not phosphorylate the Ca(2+)-ATPase appreciably in either cardiac or slow twitch muscle SR. These findings suggest a muscle-specific role for the membrane-associated CaM kinase in the modulation of Ca2+ uptake and release functions of the SR. In cardiac and slow twitch muscle, phosphorylation of the SR Ca(2+)-ATPase by CaM kinase might provide a novel mechanism for the modulation of the enzymatic and Ca2+ transport functions of this enzyme.
...
PMID:Sarcoplasmic reticulum calcium pump in cardiac and slow twitch skeletal muscle but not fast twitch skeletal muscle undergoes phosphorylation by endogenous and exogenous Ca2+/calmodulin-dependent protein kinase. Characterization of optimal conditions for calcium pump phosphorylation. 798 62

The aim of the present study was to determine the changes in phospholamban protein levels and their regulatory effect on sarcoplasmic reticulum (SR) Ca2+ uptake and left ventricular function in hypothyroid and hyperthyroid rat hearts. Hypothyroidism was associated with decreases in basal left ventricular function (+dP/dt and -dP/dt), whereas in hyperthyroidism these parameters were elevated compared with values for euthyroid hearts. The maximal SR Ca2+ uptake rates were 12.8 +/- 1.1, 15.5 +/- 1.2, and 21.4 +/- 1.4 nmol Ca2+ per milligram per minute, and the EC50 values for Ca2+ were 0.76 +/- 0.09, 0.41 +/- 0.07, and 0.30 +/- 0.05 mumol/L assayed in homogenates from hypothyroid, euthyroid, and hyperthyroid hearts, respectively. The relative tissue level of phospholamban was increased (135%) in hypothyroidism and decreased (75%) in hyperthyroidism compared with euthyroidism (100%). An opposite trend was observed for the SR Ca(2+)-ATPase, which was depressed (74%) in hypothyroid hearts but increased (134%) in hyperthyroid hearts. Consequently, the relative ratio of phospholamban to Ca(2+)-ATPase was highest in hypothyroid and lowest in hyperthyroid hearts, and these changes correlated with changes in the EC50 of the SR Ca2+ uptake for Ca2+. Stimulation of hearts with 0.1 mumol/L isoproterenol revealed that the relaxant effects were lower in hyperthyroid hearts and higher in hypothyroid hearts compared with euthyroid hearts, consistent with the alterations in the phospholamban levels. The maximal increases in the speed of relaxation, elicited by isoproterenol stimulation, correlated with the changes in the relative ratio of phospholamban to Ca(2+)-ATPase in these hearts.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Thyroid hormone-induced alterations in phospholamban protein expression. Regulatory effects on sarcoplasmic reticulum Ca2+ transport and myocardial relaxation. 803 38

The plant phenol tannin stimulated severalfold the Ca(2+)-dependent ATPase and Ca(2+)-uptake activities of dog cardiac sarcoplasmic reticulum (SR) with an EC50 value of 0.6 microM. The stimulation was due to a marked increase in the apparent affinity of the cardiac SR ATPase for Ca2+ ions while the Vmax was not affected. No stimulation of skeletal muscle SR preparations could be observed. The characteristics of stimulation were similar to those observed after phosphorylation of the regulatory protein phospholamban (PLN) by protein kinase A. The ability of protein kinase A to phosphorylate PLN was prevented by tannin with an IC50 of 3 microM. Phosphorylation of troponin I, another physiological substrate of protein kinase A, was resistant to tannin inhibition. The data show that submicromolar concentrations of tannin prevent PLN phosphorylation by interacting with the cytosolic portion of PLN. The specific binding of tannin reverses the inhibition that PLN exerts on cardiac SR ATPase.
...
PMID:Reversal of phospholamban-induced inhibition of cardiac sarcoplasmic reticulum Ca(2+)-ATPase by tannin. 806 Mar 55

Phospholamban is the regulator of the Ca(2+)-ATPase in cardiac sarcoplasmic reticulum (SR), and it has been suggested to be an important determinant in the inotropic responses of the heart to beta-adrenergic stimulation. To determine the role of phospholamban in vivo, the gene coding for this protein was targeted in murine embryonic stem cells, and mice deficient in phospholamban were generated. The phospholamban-deficient mice showed no gross developmental abnormalities but exhibited enhanced myocardial performance without changes in heart rate. The time to peak pressure and the time to half-relaxation were significantly shorter in phospholamban-deficient mice compared with their wild-type homozygous littermates as assessed in work-performing mouse heart preparations under identical venous returns, afterloads, and heart rates. The first derivatives of intraventricular pressure (+/- dP/dt) were also significantly elevated, and this was associated with an increase in the affinity of the SR Ca(2+)-ATPase for Ca2+ in the phospholamban-deficient hearts. Baseline levels of these parameters in the phospholamban-deficient hearts were equal to those observed in hearts of wild-type littermates maximally stimulated with the beta-agonist isoproterenol. These findings indicate that phospholamban acts as a critical repressor of basal myocardial contractility and may be the key phosphoprotein in mediating the heart's contractile responses to beta-adrenergic agonists.
...
PMID:Targeted ablation of the phospholamban gene is associated with markedly enhanced myocardial contractility and loss of beta-agonist stimulation. 2370 16

Phosphorylation of the sarcoplasmic reticulum (SR) protein phospholamban by adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (PKA) and Ca-calmodulin-dependent protein kinase (CaM-KII) stimulates Ca-adenosinetriphosphatase (ATPase) activity and SR Ca transport, but the role of CaM-KII-dependent phosphorylation is not well defined. We studied the PKA- and CaM-KII-dependent regulation of SR Ca transport in digitonin-permeabilized rabbit ventricular myocytes. SR Ca uptake and free Ca concentration were measured on line with indo 1 and Ca electrodes in the presence of 20 microM ruthenium red and 10 mM oxalate. neither N5,2'-w-dibutyryl-cAMP (up to 500 microM) nor the nonhydrolyzable cAMP agonist adenosine 3'5'-cyclic monophosphorothioate sodium salt (Sp-cAMP[S]; up to 275 microM) affected the maximum uptake rate (Vmax) or the dissociation constant (Kd) for Ca uptake. However, the PKA inhibitor H-89 significantly increased Kd (e.g., from 307 +/- 67 to 826 +/- 62 nM Ca at 40-65 microM H-89) without significantly affecting Vmax. Both CaM-KII inhibitors, KN-62 (60 microM) and a CaM-KII inhibitory peptide (10 microM), significantly decreased Vmax from 11.95 +/- 0.5 to 9.48 +/- 0.6 nmol.mg-1.min-1 and from 10.95 +/- 1.72 to 7.37 +/- 0.94 nmol.mg-1.min-1, respectively, without consistently changing Kd. The effects of H-89 on Kd and of KN-62 on Vmax were prevented by a monoclonal antibody to phospholamban 2D12 (consistent with the antibody removing the inhibitory effect of phospholamban on the SR Ca-ATPase).(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Protein kinase inhibitors reduce SR Ca transport in permeabilized cardiac myocytes. 806 37


<< Previous 1 2 3 4 5 6 7 8 9 10

---