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)

It is well documented that the activity of Na+,K+-ATPase can be inhibited by the arachidonic acid metabolite, 20-hydroxyeicosa-tetraenoic acid (20 HETE). Evidence is presented here that this effect is mediated by protein kinase C (PKC). PKC inhibitors abolished 20 HETE inhibition of rat Na+,K+-ATPase in renal tubular cells. 20 HETE caused translocation of PKC alpha from cytoplasm to membrane in COS cells. It also inhibited Na+,K+-ATPase activity in COS cells transfected with rat wild-type renal Na+,K+-ATPase alpha1 subunit, but not in cells transfected with Na+,K+-ATPase alpha1, where the PKC phosphorylation site, serine 23, had been mutated to alanine. PKC-induced phosphorylation of rat renal Na+,K+-ATPase, as well as of histone was strongly enhanced by 20 HETE at the physiologic calcium concentration of 1.3 microM, but not at the calcium concentration of 200 microM. The results indicate that phospholipase A2-arachidonic acid-20 HETE pathway can exert important biological effects via activation of PKC and that this effect may occur in the absence of a rise in intracellular calcium.
...
PMID:20-Hydroxyeicosa-tetraenoic acid (20 HETE) activates protein kinase C. Role in regulation of rat renal Na+,K+-ATPase. 907 30

The hepatitis C virus (HCV) nonstructural 3 protein (NS3) is a 70-kDa multifunctional enzyme with three known catalytic activities segregated in two somewhat independent domains. The essential machinery of a serine protease is localized in the N-terminal one-third of the protein, and nucleoside triphosphatase (NTPase) and helicase activities reside in the remaining C-terminal region. NS4A is a 54-residue protein expressed immediately downstream of NS3 in the viral polyprotein, and a central stretch of hydrophobic residues in NS4A form an integral structural component of the NS3 serine protease domain. There is no evidence to suggest that the two domains of NS3 are separated by proteolytic processing in vivo. This may reflect economical packaging of essential viral replicative components, but it could also mean that there is functional interdependence between the two domains. In this study, a full-length NS3-NS4A complex was isolated after expression and autoprocessing in transiently transfected COS cells. The protein was used to examine the effects of polynucleotides on the NTPase, helicase, and protease activities. Unlike the previously reported behavior of a separately expressed NS3 helicase domain, the full NS3-NS4A complex demonstrated optimal NTPase activity between pH 7.5 and 8.5. All three NS3-NS4A activities were modulated by polynucleotides, with poly(U) having the most remarkable effect. These findings suggest that the domains within NS3 may influence the activity of one another and that the interplay of HCV genomic elements may regulate the enzyme activities of this complex HCV replicase component.
...
PMID:Polynucleotide modulation of the protease, nucleoside triphosphatase, and helicase activities of a hepatitis C virus NS3-NS4A complex isolated from transfected COS cells. 909 52

Na,K-ATPase, an essential transporter of mammalian cells, is an oligomeric transmembrane protein composed of two subunits, alpha and beta, of which there are several isoforms. In this study, we demonstrate that the alpha1 and alpha2 isoforms of the Na,K-ATPase alpha subunit are modified by the covalent attachment of ubiquitin polymers in COS-7 cells. We propose that polyubiquitination of the Na,K-ATPase alpha subunit may play a role in regulating its degradation.
...
PMID:Ubiquitination of Na,K-ATPase alpha1 and alpha2 subunits. 910 5

Escherichia coli dimethyl sulfoxide reductase is a heterotrimer comprising a catalytic subunit (DmsA), an electron transfer subunit (DmsB) and an integral membrane anchor subunit (DmsC). DmsC is not antigenic and the production of antibodies to this subunit has not been successful. We have tagged DmsC at the C-terminus with a dystrophin-specific amino acid sequence (dysp) to which antibodies are readily available. We were able to use this tagging technique to monitor expression and localization of DmsC in E. coli and non-muscle eukaryotic cells. Growth properties of wild-type E. coli, strain HB101, overexpressing DmsC:dysp suggest that the expression of DmsC is lethal to E. coli. The lethality could be overcome by utilizing an E. coli F0F1 ATPase mutant as the host. Growth conditions of culture density, duration of induction, temperature of incubation after induction and media conditions were investigated to optimize DmsC:dysp accumulation levels. In order to alleviate the problem arising from the toxicity of DmsC, expression in eukaryotic tissue culture was also explored. A plasmid expressing DmsC:dysp was transfected into COS-1 or McA-RH777 cells. The presence of expressed DmsC:dysp was confirmed using specific anti-dysp antibodies and immunofluorescence microscopy analysis revealed that the DmsC:dysp was localized to the endoplasmic reticulum. Expression of DmsC:dysp did not appear to be toxic to the eukaryotic cells. These data suggest methodologies to overcome lethality problems associated with the overexpression of integral membrane proteins like DmsC.
...
PMID:Expression and epitope tagging of the membrane anchor subunit (DmsC) of Escherichia coli dimethyl sulfoxide reductase. 915 79

The enzyme Na+,K+-ATPase creates the transmembrane Na+ gradient that is of vital importance for functioning of all eukaryotic cells. Na+, K+-ATPase can be phosphorylated by protein kinase A (PKA) and protein kinase C (PKC), and these sites of phosphorylation have been identified. In the present study, we have examined the physiological significance of PKC phosphorylation of rat Na+,K+-ATPase. In COS cells transfected with wild type rat Na+,K+-ATPase alpha1, intracellular Na+ was higher and pH was lower than in cells transfected with rat Na+,K+-ATPase alpha1 in which the PKC phosphorylation site, Ser-23, had been mutated into alanine. Phorbol dibutyrate inhibited Na+,K+-ATPase-dependent ATP hydrolysis and Rb+ uptake in cells expressing wild type Na+,K+-ATPase but not in cells expressing S23A Na+,K+-ATPase. Cells expressing the S23A mutant had a more rounded appearance and attached less well to fibronectin than did untransfected cells or cells transfected with wild type rat Na+, K+-ATPase alpha1. These results indicate a functional role for PKC-mediated phosphorylation of rat Na+,K+-ATPase alpha1 and suggest a connection between this enzyme and cell adhesion.
...
PMID:Mutation of the protein kinase C phosphorylation site on rat alpha1 Na+,K+-ATPase alters regulation of intracellular Na+ and pH and influences cell shape and adhesiveness. 924 94

COS-7 cells were transiently transfected with human thyrotropin receptor and dog A1 adenosine receptor cDNAs. An A1 agonist, N6-(L-2-phenylisopropyl) adenosine (PIA), which is ineffective alone, enhanced the thyrotropin (TSH)-induced inositol phosphate production, reflecting phospholipase C (PLC) activation, but inhibited the TSH-induced cAMP accumulation, reflecting adenylyl cyclase inhibition. These PIA-induced actions were completely inhibited by pertussis toxin (PTX) treatment. Moreover, in the cells expressing a PTX-insensitive mutant of Gi2alpha or Gi3alpha, in which a glycine residue was substituted for a cysteine residue to be ADP-ribosylated by PTX, at the fourth position of the C terminus, PIA effectively exerted both stimulatory and inhibitory effects on the TSH-induced actions although the cells were treated with the toxin. Overexpression of the betagamma subunits of the G proteins enhanced the TSH-induced inositol phosphate production without any significant effect on the cAMP response; under these conditions, PIA did not further increase the elevated inositol phosphate response to TSH. On the contrary, overexpression of a constitutively active mutant of Gi2alpha, in which the guanosine triphosphatase activity is lost, inhibited the TSH-induced cAMP accumulation but hardly affected the inositol phosphate response; under these conditions, PIA never exerted further inhibitory effects on the cAMP response to TSH. In contrast to the case of the TSH-induced inositol phosphate response, the response to a constitutively active G11alpha mutant was not appreciably affected, and that to NaF was rather inhibited by PIA and overexpression of the betagamma subunits. Taken together, these results suggest that a single type of PTX-sensitive G protein mediates the A1 adenosine receptor-linked modulation of two signaling pathways in collaboration with an activated thyrotropin receptor; alpha subunits of the PTX-sensitive G proteins mediate the inhibitory action on adenylyl cyclase, and the betagamma subunits mediate the stimulatory action on PLC. In the case of the latter stimulatory action on PLC, the betagamma subunits may not directly activate PLC. The possible mechanism by which betagamma subunits enhance the TSH-induced PLC activation is discussed.
...
PMID:Betagamma subunits of pertussis toxin-sensitive G proteins mediate A1 adenosine receptor agonist-induced activation of phospholipase C in collaboration with thyrotropin. A novel stimulatory mechanism through the cross-talk of two types of receptors. 928 15

The activity of Na(+)-K(+)-ATPase can be regulated by hormones that activate adenosine 3',5'-cyclic monophosphate-dependent protein kinase (PKA). Here, using a site-directed phosphorylation state-specific antibody, we show that hormonal regulation of Na(+)-K(+)-ATPase can occur via phosphorylation of Ser-943 on its alpha-subunit. cDNAs coding for wild-type rat Na(+)-K(+)-ATPase and Na(+)-K(+)-ATPase in which the PKA phosphorylation site Ser-943 was mutated to Ala were stably and transiently transfected into COS cells. In COS cells expressing wild-type Na(+)-K(+)-ATPase the beta-adrenergic agonist isoproterenol (1 microM) significantly increased the level of phosphorylation of the alpha-subunit. Phosphorylation was accompanied by a significant inhibition of the enzyme activity, as reflected by a decrease in ATP hydrolysis and 86Rb+ transport. The effect of isoproterenol was reproduced by the PKA activator forskolin used in combination with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine and was abolished by the specific PKA inhibitor H-89. Okadaic acid, an inhibitor of protein phosphatases 1 and 2A, enhanced phosphorylation and inhibition of Na(+)-K(+)-ATPase induced by isoproterenol. The changes in activity of Na(+)-K(+)-ATPase linearly correlated with the extent of the alpha-subunit of Na(+)-K(+)-ATPase being phosphorylated. When Ser-943 was replaced by alanine, stimulation of the phosphorylation and inhibition of the activity of Na(+)-K(+)-ATPase induced by isoproterenol, alone or in combination with okadaic acid, were not observed. These results indicate that, in intact cells, modulation of the activity of Na(+)-K(+)-ATPase can be achieved by regulation of the state of phosphorylation of Ser-943. Moreover, they provide a biochemical mechanism by which beta-adrenergic agonists can regulate Na(+)-K(+)-ATPase activity.
...
PMID:PKA-mediated phosphorylation and inhibition of Na(+)-K(+)-ATPase in response to beta-adrenergic hormone. 931 10

Mutants Gly330-->Ala, Leu332-->Ala, Leu332-->Pro, and Pro780-->Ala of the alpha1-isoform of rat kidney Na+,K+-ATPase were expressed in COS-1 cells to active site concentrations between 20 and 70 pmol per mg of membrane protein. The functional properties of the mutants were characterized by titrations of Na+-, K+-, and ATP-dependencies of Na+,K+-ATPase activity as well as by a series of assays measuring the K+-dependence of the steady-state phosphoenzyme level, the kinetics of dephosphorylation under a variety of conditions, and the ADP-ATP exchange activity. In mutants Gly330-->Ala, Leu332-->Ala, and Leu332-->Pro, the molecular turnover number was reduced relative to that of the wild-type Na+,K+-ATPase, and the steady-state phosphoenzyme level was high even in the presence of several millimolar K+. At a low Na+ concentration in the absence of K+, mutants Leu332-->Pro and Gly330-->Ala displayed high ADP-ATP exchange activity and formed a high level of the ADP-sensitive phosphoenzyme (E1P). The phosphoenzyme decayed slowly following a jump in salt concentration and chase with ATP and K+. Hence, the conversion of E1P to the K+-sensitive phosphoenzyme (E2P) was inhibited in mutants Leu332-->Pro and Gly330-->Ala. In the Leu332-->Ala mutant, a high level of E2P was accumulated in the absence of K+, and the ADP-ATP exchange activity was low at low Na+ concentration in the absence of K+, but rose sharply on addition of K+. Dephosphorylation experiments indicated that in the Leu332-->Ala mutant K+ induced reversal of the phosphoenzyme interconversion, forming E1P from E2P. Leu332 is therefore a pivotal residue in the conformational change. Mutants Gly330-->Ala and Pro780-->Ala displayed reduced K+ affinities relative to the wild type, determined in three independent assays.
...
PMID:Leucine 332 at the boundary between the fourth transmembrane segment and the cytoplasmic domain of Na+,K+-ATPase plays a pivotal role in the ion translocating conformational changes. 934 Dec 23

The Na,K-ATPase is an essential plasma membrane transporter of mammalian cells composed of two subunits, alpha and beta, of which there are several isoforms. We investigated the effect of a substitution, S364P, on the subcellular localization and enzymatic activity of the wild-type alpha2 and alpha2L111R,N122D (alpha2RD) subunits. The substitutions, L111R and N122D, lower the affinity of the alpha2 subunit for the inhibitor ouabain roughly one thousand-fold (E. A. Jewell and J. B. Lingrel, J. Biol. Chem. 266, 16925-16930, 1991) and were introduced into the alpha2 subunit to distinguish its enzymatic activity from that of the endogenous alpha1 subunit of COS-7 cells. The S364P substitution is located in the ATP binding site, only five residues from the aspartyl residue which is phosphorylated during the catalytic cycle of the Na,K-ATPase. This substitution dramatically decreases the amount of enzymatic activity associated with expression of the alpha2RD subunit. Despite the fact that S364P substitution does not block association of the alpha2RD subunit with the endogenous beta1 subunit, it prevents the alpha2 and alpha2RD subunits from accumulating in the plasma membrane and results in their localization in the endoplasmic reticulum.
...
PMID:Intracellular localization of Na,K-ATPase alpha2 subunit mutants. 934 79

Basic fibroblast growth factor (FGF-2) is one of a select group of proteins that can exit cells through an alternate, endoplasmic reticulum/Golgi apparatus independent exocytic pathway. This alternate pathway has been termed protein export. In an attempt to better understand this process, we have identified a family of related compounds, "cardenolides," that inhibit FGF-2 export. The cardenolides inhibit FGF-2 export in a time and concentration dependent fashion. Inhibition of FGF-2 export is specific in that the cardenolides have no effect on conventional protein secretion as measured by their inability to block release of the secreted protein human chorionic gonadotropin-alpha. Because cardenolides are known to inhibit ion transport activity mediated by Na+,K+-ATPase, we investigated whether there are functional interactions between FGF-2 and their only known molecular target: the alpha-subunit of Na+, K+-ATPase. Export of FGF-2 from COS-1 cells is selectively inhibited when co-transfected with expression vectors encoding the alpha-subunit and FGF-2. Moreover, antibodies to the alpha-subunit specifically co-immunoprecipitate FGF-2 along with the alpha-subunit while conversely, antibodies to FGF-2 specifically co-immunoprecipitate the alpha-subunit along with FGF-2. Finally, the ion transporting activities of the Na+,K+-ATPase can be uncoupled from protein export. Varying the external concentration of K+ has little effect on export of FGF-2. Taken together, these data: 1) identify a novel activity for cardenolides; 2) suggest a previously unknown role for the alpha-subunit of Na+, K+-ATPase in FGF-2 export; and 3) raise the possibility that the alpha-subunit itself may be an integral component of this alternate exocytic pathway mediating translocation of cytosolic FGF-2 to the cell surface.
...
PMID:The inhibition of fibroblast growth factor-2 export by cardenolides implies a novel function for the catalytic subunit of Na+,K+-ATPase. 941 14


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

---