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)

Left ventricular hypertrophy may lead to heart failure. The transition between hypertrophy and heart failure is, however, incompletely understood. On the cellular level, human heart failure is characterized by alterations in Ca(2+)-cycling proteins and beta-adrenergic receptor density, but the hypertrophied human heart remains largely under studied. In this investigation, 21 donor hearts which could not be used for transplantation were studied. Ten of these hearts came from organ donors with documented left ventricular hypertrophy and normal cardiac function. Eleven of the hearts were non-failing, obtained from individuals with no evidence of cardiac disease. Nine failing hearts from transplant recipients were also studied. beta-adrenergic receptor density was determined by radioligand binding. mRNA for atrial natriuretic factor, calsequestrin, sarcoplasmic reticulum Ca(2+)-ATPase, and phospholamban was measured by Northern blot. Actin, calsequestrin, sarcoplasmic reticulum Ca(2+)-ATPase, and phospholamban proteins were quantified by Western blot. In both hypertrophied and failing ventricles, mRNA for atrial natriuretic factor was expressed, as compared to no expression in non-failing hearts. In failing hearts, beta -adrenergic receptor density and both mRNA and protein levels of the Ca(2+)-ATPase were significantly decreased v non-failing hearts. By comparison, hypertrophied hearts showed a reduction in mRNA expression for both the Ca(2+)-ATPase and phospholamban with no change in the corresponding protein levels, and no change in beta-receptors. These data suggest that the previously demonstrated reduction in beta-adrenergic receptors and Ca(2+)-cycling proteins in the failing human heart may be features of the decompensated state, but are not found in human hearts with left ventricular hypertrophy and preserved systolic function.
J Mol Cell Cardiol 2001 Jun
PMID:Beta-adrenergic receptors and calcium cycling proteins in non-failing, hypertrophied and failing human hearts: transition from hypertrophy to failure. 1144 30

The aim of the study was to find out whether low phospholamban level in atria as compared with ventricles is associated with differences in sarcoplasmic reticular Ca2+-uptake and contractile performance. Relationship between phospholamban and beta-adrenergic stimulation in rat left atria and papillary muscles were examined by means of contractile measurements, sarcoplasmic reticular oxalate-supported Ca2+-uptake, and Western blotting of phosphorylated phospholamban. Phosphoprotein determination after beta-adrenergic stimulation demonstrated that the levels of Ser16 and Thr17 phosphorylated phospholamban in atria remained at about one-third of that in ventricles. However, comparison of sarcoplasmic reticular Ca2+-uptake in control and isoproterenol perfused preparations demonstrated that the effect of beta-adrenergic stimulation on sarcoplasmic reticular Ca2+-uptake was stronger in atrial preparations. Moreover, atria responded to isoproterenol with much larger increases in developed tension, contractility and relaxation rates than papillary muscles. Thus, despite lower level of phospholamban, the beta-adrenergic activation of sarcoplasmic reticular Ca2+-uptake and contractile indices are higher in atria.
Mol Cell Biochem 2001 Jul
PMID:Decreased expression of phospholamban is not associated with lower beta-adrenergic activation in rat atria. 1168 11

The regulation of calcium levels across the membrane of the sarcoplasmic reticulum involves the complex interplay of several membrane proteins. Phospholamban is a 52 residue integral membrane protein that is involved in reversibly inhibiting the Ca(2+) pump and regulating the flow of Ca ions across the sarcoplasmic reticulum membrane during muscle contraction and relaxation. The structure of phospholamban is central to its regulatory role. Using homonuclear rotational resonance NMR methods, we show that the internuclear distances between [1-(13)C]Leu7 and [3-(13)C]Ala11 in the cytoplasmic region, between [1-(13)C]Pro21 and [3-(13)C]Ala24 in the juxtamembrane region and between [1-(13)C]Leu42 and [3-(13)C]Cys46 in the transmembrane domain of phospholamban are consistent with alpha-helical secondary structure. Additional heteronuclear rotational-echo double-resonance NMR measurements confirm that the secondary structure is helical in the region of Pro21 and that there are no large conformational changes upon phosphorylation. These results support the model of the phospholamban pentamer as a bundle of five long alpha-helices. The long extended helices provide a mechanism by which the cytoplasmic region of phospholamban interacts with residues in the cytoplasmic domain of the Ca(2+) pump.
J Mol Biol 2001 Nov 09
PMID:Helical structure of phospholamban in membrane bilayers. 1170 69

A systematic transition from chronic stunning to hibernation occurs as coronary flow reserve decreases to a critical level. Hibernating myocardium exhibits apoptosis-induced myocyte loss and a reduction in the expression of the sarcoplasmic reticulum (SR) Ca2+ ATPase but whether similar cellular changes occur in chronic stunning is unknown. Pigs with a chronic left anterior descending coronary artery (LAD) stenosis were studied one (n=9) or two (n=10) months after instrumentation. Anterior hypokinesis with normal levels of resting perfusion developed at each time-point, consistent with chronic stunning. After 1 month, sub-endocardial flow reserve was moderately reduced (adenosine/rest, LAD: 3.60+/-0.91 v Remote: 6.00+/-0.54, P<0.01) with no regional differences in SR protein expression, no increase in apoptosis (32+/-6 v 21+/-5 nuclei/10(6) myocyte nuclei, p-ns) and no regional myocyte loss (1976+/-44 v 1955+/-30 nuclei/mm2, p-ns). After 2 months, sub-endocardial flow reserve in chronically stunned myocardium was severely impaired (LAD: 1.41+/-0.21 v Remote: 5.59+/-0.96, P<0.01). There were small but significant reductions in LAD mRNA and protein levels for the SRCa2+ ATPase and phospholamban whereas calsequestrin was unchanged. In addition, regional myocyte apoptosis increased (127+/-24 v 55+/-9 nuclei/10(6) myocyte nuclei, P<0.01), resulting in the onset of myocyte loss (1293+/-50 v 1394+/-32 nuclei/mm2, P<0.01). Apoptosis-induced myocyte loss and reductions in SR protein expression are not invariably present in viable chronically dysfunctional myocardium. They are induced as the propensity of a region to develop reversible ischemia increases (as reflected by coronary flow reserve). The temporal progression indicates that alterations in SR protein expression and myocyte apoptosis precede the transition from chronically stunned to hibernating myocardium.
J Mol Cell Cardiol 2001 Nov
PMID:Myocyte apoptosis and reduced SR gene expression precede the transition from chronically stunned to hibernating myocardium. 1170 39

Sarcoplasmic reticulum (SR) dysfunction is one of the multiple alterations that occurs in ischemia-reperfused hearts. Because SR function is regulated by phosphorylation of phospholamban (PLB), a SR protein phosphorylated by cAMP-dependent protein kinase (PKA) at Ser(16)and Ca(2+)-calmodulin-dependent protein kinase (CaMKII) at Thr(17), the phosphorylation of these residues during ischemia and reperfusion was examined in Langendorff-perfused rat hearts. Ser(16)phosphorylation increased significantly after 20 min of ischemia from 2.5+/-0.6% to 99.8+/-25.5% of maximal isoproterenol-induced site-specific phosphorylation and decreased to control values immediately after reperfusion. Thr(17)phosphorylation transiently increased at 2-5 min of ischemia and at 1 min of reperfusion (R1, 166.2+/-28.2%). The ischemia-induced increase in Ser(16)phosphorylation was significantly diminished in hearts from catecholamine-depleted animals and/or after beta-blockade and abolished in the presence of the PKA-inhibitor, H-89. Thr(17)phosphorylation at the beginning of ischemia was blunted by nifedipine, whereas at R1 it was significantly diminished by perfusion with 0 m m Ca(2+)in the presence of EGTA and by the Na(+)/Ca(2+)exchanger inhibitor KB-R7943. KN-93, used to specifically inhibit CaMKII, decreased Thr(17)phosphorylation at R1 and significantly prolonged half relaxation time. The results demonstrated a dissociation between the phosphorylation of PLB sites, being phosphorylation of Ser(16)dependent on the beta-adrenergic cascade during ischemia and phosphorylation of Thr(17)on Ca(2+)influx both, at the beginning of ischemia and reperfusion. Phosphorylation of Thr(17)at the onset of reflow may provide the cell a mechanism to cope with Ca(2+)overload, transiently favoring the recovery of relaxation during early reperfusion.
J Mol Cell Cardiol 2002 Jan
PMID:Time course and mechanisms of phosphorylation of phospholamban residues in ischemia-reperfused rat hearts. Dissociation of phospholamban phosphorylation pathways. 1181 63

Compromised SERCA 2a activity is a key malfunction leading to the Ca(2+) cycling alterations in failing human myocardium. SERCA 2a activity is regulated by the Ca(2+)/calmodulin-dependent protein kinase (CaM-kinase) but alterations of the CaM-kinase pathway regarding SERCA 2a in heart failure are unresolved. Therefore we investigated the CaM-kinase and phosphatase calcineurin mediated regulation of SERCA 2a in failing and non-failing human myocardium. We studied human myocardial preparations from explanted hearts from non-failing organ donors (NF, n=8) and from patients with terminal heart failure undergoing cardiac transplantation (dilated cardiomyopathy, DCM, n=8). SERCA 2a activity was determined using a NADH-coupled enzyme assay [expressed in nmol ATP/(mg protein x min)] and by(45)Ca(2+) uptake. Protein expression of SERCA 2a, phospholamban, calsequestrin and calcineurin was assessed by Western blotting (expressed as densitometric units/microg protein); phosphorylation of cardiac proteins was detected with specific phospho-antibodies for phospholamban at threonine-17 (PT17) or by incorporation of [gamma -(32)P] (expressed as pmol(32)P/mg). Maximal(45)Ca(2+) uptake (in pmol/mg/min) (NF: 3402+/-174; DCM: 2488+/-189) and maximal SERCA 2a activity were reduced in DCM compared to NF (V(max): NF: 125+/-9; DCM: 98+/-5). The V(max) reduction could be mimicked by calcineurin in vitro in NF (NF(control): 72.1+/-3.7; NF(+calcineurin): 49.8+/-2.9) and restored in DCM by CaM-kinase in vitro (DCM(control): 98+/-5; DCM(+CaM-kinase): 120+/-6). Protein expression of SERCA 2a, phospholamban and calsequestrin remained similar, but calcineurin expression was significantly increased in failing human hearts (NF: 11.6+/-1.5 v DCM: 17.1+/-1.6). Although the capacity of endogenous CaM-kinase to phosphorylate PT17 was significantly higher in DCM (DCM(control): 128+/-36; DCM(+endogenous CaM-kinase): 205+/-20) compared to NF myocardium (NF(control): 273+/-37; NF(+endogenous CaM-kinase): 254+/-31), net phosphorylation at threonine-17 phospholamban was significantly lower in DCM (DCM 130+/-11 v NF 170+/-11). A calcineurin-dependent dephosphorylation of phospholamban could be mimicked in vitro by incubation of NF preparations with calcineurin (NF(control) 80.7+/-4.4 v NF(+calcineurin) 30.7+/-4.1, P<0.05). In human myocardium, the V(max) of SERCA 2a and the phosphorylation of phospholamban is modulated by CaM-kinase and calcineurin, at least in vitro. In failing human myocardium, despite increased CaM-kinase activity, calcineurin dephosphorylation leads to decreased net phosphorylation of threonine-17 phospholamban in vivo. Increased calcineurin activity contributes to the impaired V(max) of SERCA 2a in failing human myocardium and the disorder in Ca(2+)-handling in heart failure.
J Mol Cell Cardiol 2002 Mar
PMID:Evidence for calcineurin-mediated regulation of SERCA 2a activity in human myocardium. 1194 24

Frequency-dependent acceleration of relaxation (FDAR) is an intrinsic physiological mechanism, which allows more rapid ventricular diastolic filling at higher heart rates. FDAR is also observed in isolated myocardial trabeculae and cardiac myocytes, but its mechanism is still poorly understood. We tested the hypothesis that FDAR results mainly from Ca/calmodulin-dependent protein kinase II (CaMKII) dependent stimulation of sarcoplasmic reticulum (SR) Ca transport, but does not require phospholamban. Experiments were performed at 23 or 35 degrees C in isolated ventricular muscle and single myocytes from wild-type (WT) and phospholamban knockout (PLB-KO) mice and rat ventricular myocytes. Isometric twitch force of muscles and unloaded shortening and Ca transients in myocytes were measured ([Ca](o)=1mM) in the absence and presence of CaMKII inhibitors (1 microM KN-93 or 20 microM autocamtide-2 related inhibitory peptide, AIP). Stimulation frequency was altered over a wide range (0.2-8Hz) and post-rest vs steady state twitches were also compared. In both WT and PLB-KO mouse muscles FDAR of twitch force was prominent, but was largely suppressed by KN-93. FDAR of twitch contractions was associated with FDAR of Ca transients in PLB-KO myocytes, and both were inhibited by KN-93. Similarly, a different CaMKII inhibitor (AIP) inhibited FDAR of contraction and Ca transients in rat ventricular myocytes. We conclude that FDAR results mainly from CaMKII-dependent stimulation of SR Ca transport, but does not require phospholamban.
J Mol Cell Cardiol 2002 Aug
PMID:Frequency-dependent acceleration of relaxation in the heart depends on CaMKII, but not phospholamban. 1223 67

Rapid atrial pacing produces atrial systolic and diastolic failure characterized by absent atrial booster pump function, increased atrial chamber stiffness, enhanced atrial conduit function, and atrial enlargement. However, the processes underlying these abnormalities are poorly understood. Therefore, we examined left atrial myocardium from dogs with rapid pacing-induced atrial failure (400 bpm for 6 weeks) and from control dogs. Western blotting was used to determine the levels of proteins involved in calcium homeostasis (SERCA 2A, phospholamban, Na+-Ca2+ exchanger). Matrix metalloproteinase (MMP) activity was measured using gelatin and casein zymography, and levels of tissue inhibitor of metalloproteinase-4 (TIMP-4) and the TIMP-4 complexed with MMPs were measured with Western blot analysis. There were no differences in SERCA 2A or Na+-Ca2+ exchanger protein levels, but phospholamban level was significantly decreased in atrial samples from rapidly paced dogs (51.2 +/- 7.8 vs. 77.0 +/- 10.0, p < 0.01). The activity of MMP-9 was selectively and significantly increased by approximately 50%, and the level of complexed TIMP-4 protein was significantly decreased by approximately 50% in samples from dogs with atrial failure. Thus, rapid pacing-induced atrial failure is associated with differential changes in MMP activity, an unchanged number of calcium pumps, and compensatory changes in the level of phospholamban.
Mol Cell Biochem 2002 Sep
PMID:Remodeling of the left atrium in pacing-induced atrial cardiomyopathy. 1234 2

In an Ohmic model, channel conductivity can be described in terms of the geometry of a conducting cable. The essential features of such devices are the arc length of the curve describing the channel's longitudinal path, and the cross-sectional areas transversal to this curve. In a first approximation, conducting channels can be represented by an average molecular shape with estimated lengths and cross-sectional areas. Whereas the physical shortcomings of this approach are known, its accuracy limitations in practice have not been established. In this work, we discuss an improved model for the channel's shape, one that allows us to gauge how much of the Ohmic conductivity can be assigned purely to geometrical features. In the present algorithm, we investigate all regions inside the pore that are accessible to ions using various choices for the molecular surface of the inner channel. We discuss the agreement with experimental conductances in the case of 12 channels (cholera toxin B-subunit pentamer, Staphylococcus aureus alpha-hemolysin, Streptomyces lividans KcsA channel, seven porins, gramicidin A, and phospholamban). Our results can be regarded as a benchmark for the best performance that can be expected from a geometrical model of conductance. Consequently, significant deviations from experimental trends can safely be assigned to non-geometrical factors, namely the specific composition of the ion channel and the detailed electrostatic interactions between the channel and a particular ion.
J Mol Graph Model 2002 Oct
PMID:Geometrical modelling of Ohmic conductance in ion channels. 1239 41

We describe an effective procedure for modeling the structures of simple transmembrane helix homo-oligomers. The method differs from many previous approaches in that the only structural constraint we use to help select the correct model is the oligomerization state of the protein. The method involves the following steps: (1) perform 100-250 independent Monte Carlo energy minimizations of helix pairs to produce a large collection of well-packed structures; (2) filter the minimized structures to find those that are consistent with the expected symmetry of the oligomer; (3) cluster the structures that pass the symmetry filter; and (4) select a representative of the most populous cluster as the final prediction. We applied the method to the transmembrane helices of five proteins and compare our results to the available experimental data. Our predictions of glycophorin A, neu, the M2 channel and phospholamban resulted in a single model for each protein that agreed with the experimental results. In the case of erbB-2, however, we obtained three structurally distinct clusters of approximately equal sizes, so it was not possible to identify a clearly favored structure. This may reflect a real heterogeneity of packing modes for erbB-2, which is known to interact with different receptor subunits. Our method should be useful for obtaining structural models of transmembrane domains, improving our understanding of structure/function relationships for particular membrane proteins.
J Mol Biol 2003 Jun 13
PMID:A simple method for modeling transmembrane helix oligomers. 1278 81


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