Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adenosine has several potentially cardioprotective effects including vasodilatation, reduction in heart rate and alterations in metabolism. Adenosine inhibits catecholamine-induced increase in contractile function mainly through inhibition of phosphorylation of phospholamban (PLB), the main regulatory protein of Ca(2+)-ATPase in sarcoplasmic reticulum (SR), and during ischemia it reduces calcium (Ca2+) overload. In this study we examined the effects of endogenous adenosine on contractile function and metabolism during low-flow ischemia (LFI) and investigated whether endogenous adenosine can alter expression of the Ca(2+)-ATPase/PLB-system and other Ca(2+)-regulatory proteins. Isolated blood-perfused piglet hearts underwent 120 min 10% flow. Hearts were treated with either saline, the adenosine receptor blocker (8)-sulfophenyl theophylline (8SPT, 300 micromol/l) or the nucleoside transport inhibitor draflazine (1 micromol/l). During LFI, 8SPT did not substantially influence metabolic or functional responses. However, draflazine enhanced the reduction in heart rate, contractile force and MVO(2), with less release of H+ and CO2. Before LFI there were no significant differences between groups for any of the proteins (Ca(2+)-ATPase, ryanodine-receptor, Na+/K(+)-ATPase) or mRNAs (Ca(2+)-ATPase, PLB, calsequestrin, Na+/Ca(2+)-exchanger) measured. At end of LFI mRNA-level of PLB was higher in draflazine-treated hearts compared to both other groups (P<0.01 vs both). Also, at end of LFI protein-level of Ca(2+)-ATPase was lower in draflazine-treated hearts (P<0.05 vs both), and a parallel trend towards a lower mRNA-level was seen (P=0.11 vs saline and P=0.43 vs 8SPT). During LFI tissue Ca2+ tended to rise in saline- and 8SPT-treated hearts but not in draflazine-treated hearts (at end of LFI, P=0.01 vs 8SPT). We conclude that the amount of adenosine normally produced during LFI does not substantially influence function and metabolism. However, increased endogenous levels by draflazine enhance downregulation of function and reduce signs of anaerobic metabolism. At end of LFI associated changes in expression of PLB and Ca(2+)-ATPase were seen. The functional significance was not determined in the present study. However, altered protein-levels might influence Ca(2+)-handling in sarcoplasmic reticulum and thus affect contractile force and tolerance to ischemia.
J Mol Cell Cardiol 1999 Oct
PMID:Elevated levels of endogenous adenosine alter metabolism and enhance reduction in contractile function during low-flow ischemia: associated changes in expression of Ca(2+)-ATPase and phospholamban. 1052 27

Twelve mice with PLB overexpression (PLBOE), and 11 isogenic FVB/N wild-type (WT) controls, were anesthetized and instrumented with a 1.4 F Millar catheter in the LV and a 1 F pacemaker in the right atrium. At a cycle length of 200 ms and a fixed extrastimulus of 120 ms, extrastimuli with increasing intervals (PESI) up to 1000 ms were introduced, and the peak rates of LV isovolumic contraction (+/- dP/dtmax) were normalized and fit to monoexponential equations. In a subset of animals, the protocols were repeated after ryanodine (4 ng/g) was given to deplete SR Ca2+ stores. The time constant and the plateau of the exponential curve fits were significantly greater in PLBOE than WT (107.8 +/- 7.0 v 75.2 +/- 5.5 ms and 1.39 +/- 0.03 v 1.08 +/- 0.02, both P < 0.05). At 200, 600 and 1000 ms, the normalized dP/dt was significantly greater in PLBOE than WT. After ryanodine, normalized dP/dt was significantly decreased in PLBOE, but unchanged in WT. The protein levels of the sodium-calcium exchanger normalized to calsequestrin were increased 3.7 +/- 0.3-fold in PLBOE compared to controls. In conclusion, the phospholamban level is a critical determinant of postextrasystolic potentiation in this transgenic model, and is differentially impaired by ryanodine at long diastolic intervals in PLBOE v controls. These differences may be due in part to changes in the protein level and resultant activity of the sodium calcium exchanger.
J Mol Cell Cardiol 1999 Nov
PMID:Influence of transgenic overexpression of phospholamban on postextrasystolic potentiation. 1059 Oct 27

Phospholamban is a major regulator of cardiac diastole, with alterations in expression associated with modified cardiac relaxation. To study transcriptional regulation of phospholamban expression, we made reporter constructs that expressed luciferase under control of putative promoter sequences from the rat phospholamban gene. When transfected into neonatal rat cardiomyocytes, constructs containing at least 159 nucleotides preceding the transcription start site were equally active, while truncation to -66/+64 removed all promoter activity. Constructs were more active in cardiomyocytes than in HeLa cells (which do not express phospholamban), but did not show absolute cell-type specificity of expression. Addition of sequences upstream to -4032, all of the intron (7.4 kb), or 3'UTR sequences (0. 8 kb) did not enhance cell-specific expression. To focus on the basal promoter region (-159/-66), a series of deletion constructs were made that identified a novel 35 bp region (-159/-125; Phospholamban Promoter Element 1, PPE1) required for promoter activity in cardiomyocytes. Site-specific mutations identified nucleotides -150/-133 as containing most of the promoter-enhancing activity. While the rat PPE1 is highly conserved (>70%) in four other mammalian phospholamban genes, it does not contain previously characterized regulatory elements. In cardiomyocytes the PPE1 sequence markedly enhanced activity of the SV40 early promoter. A conserved CCAAT element (-83/-79) was also required for promoter activity in both cardiomyocytes and HeLa cells. Exonuclease III footprinting identified protein/DNA interactions in both the extended CCAAT box and PPE1 domains. Gel shift studies identified the CCAAT elements as binding CBF/NF-Y.
J Mol Cell Cardiol 1999 Dec
PMID:Characterization of proximal transcription regulatory elements in the rat phospholamban promoter. 1064 Apr 42

The purpose of this study was to evaluate the early changes in sarcoplasmic reticulum (SR) function and the parallel morphological and hemodynamic modifications occurring in the heart following pressure overload. As regards SR function, we also explored the levels of acylphosphatase, an enzyme which might have a regulatory effect on the SR Ca(2+) pump by hydrolyzing the phosphorylated intermediate of this transport system. Pigs subjected to pressure overload by aortic stenosis for 6, 12, 24, 48, 72, and 96 h were compared to sham-operated controls. At each of the considered times both SR Ca(2+)-ATPase activity and Ca(2+) uptake, as well as acylphosphatase activity, were significantly enhanced in the pressure overloaded compared to the control hearts, with a maximal increase at 6 h; moreover, a positive and significant correlation was found between these parameters. The modifications in the activities of Ca(2+)-ATPase and acylphosphatase reflected an increased expression of these proteins, while phospholamban did not show significant changes in its concentration nor in its phosphorylation status. As for hemodynamic parameters, rapid changes in the left ventricular function were observed and especially the early hours following the aortic stenosis appeared to be crucial for the adjustment of heart function. The most relevant morphological finding was a focal disarrangement of the myofibrillar pattern which was very evident at 6 h, and progressively attenuated at later times. Taken together our data suggest that an early adaptation to the increased hemodynamic working overload is a consistent activation of the contractile apparatus which reflects, at least in part, an enhanced SR function. Besides the changes in Ca(2+) pump protein expression, increased acylphosphatase levels might also contribute to this effect.
J Mol Cell Cardiol 2000 Jan
PMID:Early changes induced in the left ventricle by pressure overload. An experimental study on swine heart. 1065 97

The transcriptional regulation of an isolated rat phospholamban (PL) promoter fragment in rat cardiomyocytes was analyzed by applying a new method to reach substantially higher transfection efficiencies: gene gun biolistics. The gene gun transfection method was optimized for application to primary cultures of rat neonatal cardiomyocytes. Cells, cultured at different densities (0.75-1.50x10(5)cells/cm(2)) in serum-free medium, were transfected with DNA coated gold particles. A transfection efficiency of up to 10% could be achieved (compared to <1% with other methods) by the gene gun as checked using a RSV- beta-Gal construct. Cardiomyocytes were stimulated by endothelin-1 (ET-1) (10(-8)M) to induce hypertrophy, thereby yielding the characteristic changes in gene expression (upregulation of Atrial Natriuretic Factor (ANF) and downregulation of PL). The basal activity of an ANF promoter fragment (increasing from the lowest to highest density 2.6-fold) and its ET-1 inducibility (only significant upregulation of 2.6-fold, at lowest density) appeared to be dependent on the plating density of the cardiomyocytes. A PL promoter fragment was isolated, sequenced and 1.4 kb was subcloned in a luciferase reporter vector. The basal activity of the PL promoter fragment was not dependent on the plating density. ET-1 did not downregulate the PL promoter, rather a significant upregulation (1.4-fold) was found at the highest plating density. In conclusion, plating density of the cardiomyocytes can influence promoter activity as shown with an ANF promoter fragment. A newly isolated and sequenced rat PL promoter fragment did not direct gene expression as expected on basis of downregulation of the PL gene by ET-1 observed in this model.
J Mol Cell Cardiol 2000 Feb
PMID:Endothelin-1 responsiveness of a 1.4 kb phospholamban promoter fragment in rat cardiomyocytes transfected by the gene gun. 1072 6

The mouse has been used extensively for generating transgenic animal models to study cardiovascular disease. Recently, a number of transgenic mouse models have been created to investigate the importance of sarcoplasmic reticulum (SR) Ca(2+)transport proteins in cardiac pathophysiology. However, the expression and regulation of cardiac SR Ca(2+)ATPase and other Ca(2+)transport proteins have not been studied in detail in the mouse. In this study, we used multiplex RNase mapping analysis to determine SERCA2, phospholamban (PLB), and Na(+)/Ca(2+)-exchanger (NCX-1) gene expression throughout mouse heart development and in hypo/hyperthyroid animals. Our results demonstrate that the expression of SERCA2 and PLB mRNA increase eight-fold from fetal to adult stages, indicating that SR function increases with heart development. In contrast, the expression of the Na(+)/Ca(2+)-exchanger gene is two-fold higher in fetal heart compared to adult. Our study also makes the important observation that in hypothyroidic hearts the NCX-1 mRNA and protein levels were upregulated, whereas the SERCA2 mRNA/protein levels were downregulated. In hyperthyroidic hearts, however, an opposite response was identified. These findings are important and point out that the expression of NCX-1 is regulated antithetically to that of SERCA2 during heart development and in response to alterations in thyroid hormone levels.
J Mol Cell Cardiol 2000 Mar
PMID:The expression of SR calcium transport ATPase and the Na(+)/Ca(2+)Exchanger are antithetically regulated during mouse cardiac development and in Hypo/hyperthyroidism. 1073 44

The diabetic heart has an abnormal intracellular calcium ([Ca(2+)]i) metabolism. However, the responsible molecular mechanisms are unclear. The present study aimed to investigate mRNAs expressed in the proteins which regulate heart [Ca(2+)]i metabolism in streptozotocin (STZ)-induced diabetic rats. Expression of sarcoplasmic reticulum Ca(2+)-adenosine triphosphatase (SR Ca(2+)-ATPase) mRNA was significantly less in the heart 3 weeks after STZ injection than that in the age-matched controls. Together with the down-regulation of SR Ca(2+)-ATPase, expression of ryanodine sensitive Ca(2+)channel (RYR) mRNA was also decreased 12 weeks after STZ injection. Insulin supplementation fully restored the decreased mRNAs expression of SR Ca(2+)-ATPase and RYR. The diminished expression and restoration with insulin supplementation of SR Ca(2+)-ATPase was further confirmed at the protein level. In contrast, expression of mRNAs coding the L-type Ca(2+)channel, Na(+)-Ca(2+)exchanger, or phospholamban were not affected 3 or 12 weeks after STZ injection. These results can be taken to indicate that the down-regulation of SR Ca(2+)-ATPase and RYR mRNAs is a possible underlying cause of cardiac dysfunction in STZ-induced diabetic rats.
J Mol Cell Cardiol 2000 Apr
PMID:Diminished expression of sarcoplasmic reticulum Ca(2+)-ATPase and ryanodine sensitive Ca(2+)Channel mRNA in streptozotocin-induced diabetic rat heart. 1086 Nov 37

A structural model of pentameric phospholamban (Plb) in a lipid bilayer has been derived using a combination of experimental data, obtained from ATR-FTIR site-directed dichroism, and the implementation of the resulting restraints during a molecular dynamics simulation. Plb (residues 24-52) has been synthesised incorporating a new label, 1-(13)C==(18)O, at residues 42 and 43. We have not only determined the tilt of the helices, 10(+/-6) degrees, but also the relative orientation of the transmembrane segments, with an omega angle of -32(+/-10) degrees for L42. This angle is taken as zero in the direction of the helix tilt. Plb is a simple test case where site-directed dichroism has been applied to resolve the indeterminacy arising from the mutagenesis data available. The results presented point specifically to a single structural model for Plb.
J Mol Biol 2000 Jul 21
PMID:Use of a new label, (13)==(18)O, in the determination of a structural model of phospholamban in a lipid bilayer. Spatial restraints resolve the ambiguity arising from interpretations of mutagenesis data. 1089 Dec 62

Progressive deterioration of cardiac contractility is a central feature of congestive heart failure (CHF) in humans. In this report we review those studies that have addressed the idea that alterations of intracellular calcium (Ca(2+)) regulation is primarily responsible for the depressed contractility of the failing heart. The review points out that Ca(2+)transients and contraction are similar in non-failing and failing myocytes at very slow frequencies of stimulation (and other low stress environments). Faster pacing rates, high Ca(2+)and beta-adrenergic stimulation reveal large reductions in contractile reserve in failing myocytes. The underlying cellular basis of these defects is then considered. Studies showing changes in the abundance of L-type Ca(2+)channels, Ca(2+)transport proteins [sarcoplasmic reticulum Ca(2+)ATPase (SERCA2), phospholamban (PLB), Na(+)/Ca(2+) exchanger (NCX)] and Ca(2+) release channels (RYR) in excitation-contraction coupling and Ca(2+)release and uptake by the sarcoplasmic reticulum (SR) are reviewed. These observations support our hypotheses that (i) defective Ca(2+)regulation involves multiple molecules and processes, not one molecule, (ii) the initiation and progression of CHF inolves defective Ca(2+)regulation, and (iii) prevention or correction of Ca(2+)regulatory defects in the early stages of cardiac diseases can delay or prevent the onset of CHF.
J Mol Cell Cardiol 2000 Sep
PMID:Abnormalities of calcium cycling in the hypertrophied and failing heart. 1096 23

Stress-responsive p38 MAP kinase is activated by phosphorylation during global and severe regional myocardial ischemia. However, it is unknown whether or not moderate, low-flow ischemia also activates p38 MAP kinase. Therefore, we investigated p38 MAP kinase activation in an established model of short-term hibernation and stunning. In anesthetized swine, coronary blood flow into the left anterior descending coronary artery was decreased in order to reduce regional contractile function by identical with 50%. Transmural myocardial biopsies were taken before (controls) and during ischemia as well as after reperfusion. Creatine phosphate content, after an early ischemic reduction, recovered to control values at 90 min ischemia. The expression of phospholamban, SERCA2a, calsequestrin, and troponin inhibitor was unchanged under these conditions (Northern and Western blotting). At 8 min of ischemia, however, p38 MAP kinase was activated to 221% of the pre-ischemic value as judged by its elevated phosphorylation state. Then, it returned to control values by 85 min ischemia. We conclude that low-flow ischemia transiently activates the stress-responsive p38 MAP kinase which might act to trigger cardioprotective events.
J Mol Cell Cardiol 2000 Oct
PMID:The stress-responsive MAP kinase p38 is activated by low-flow ischemia in the in situ porcine heart. 1101 23


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