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)

Expression of Na,K-ATPase catalytic alpha isoform (alpha 1, alpha 2, and alpha 3) and beta subunit genes in rodent muscle was investigated using the murine C2C12 myogenic cell line. RNA blot analyses of myoblasts revealed expression primarily of the alpha 1 mRNA and low levels of alpha 2 mRNA. Fusion of the proliferating myoblasts to form myotubes was accompanied by an approximate 12-fold induction of the alpha 2 mRNA. In contrast, expression of alpha 1 mRNA remained constant throughout myogenesis. The alpha 3 mRNA was not detected in either myoblasts or myotubes. The beta mRNA abundance also increased 2-3-fold during myotube formation. In rodent tissues, low and high affinity cardiac glycoside (e.g. ouabain) receptors have been shown to be associated with the Na,K-ATPase catalytic alpha 1 and alpha 2 isoform subunits, respectively. The existence of these two functional classes of Na,K-ATPase in myoblasts and myotubes correlated with the biphasic ouabain inhibition of Na,K-ATPase activity. Confluent myoblasts expressed primarily the alpha 1 isozyme (IC50 = 3.6 X 10(-5) M; 95% of total activity) and lesser amounts of the alpha 2 isozyme (IC50 = 1.1 X 10(-7) M; 5% of total activity). In contrast, the myotubes showed significant levels of the alpha 1 isozyme (IC50 = 4.0 X 10(-5) M; 68% of total activity) and, in addition, showed a 6-fold increase in the relative levels of the alpha 2 isozyme (IC50 = 1.1 X 10(-7) M; 32% of total activity). To quantitate further the expression of the high affinity, ouabain-sensitive alpha 2 isozyme, a whole cell [3H]ouabain-binding assay was used. Results revealed that myotubes have an approximately 6-fold greater concentration of [3H]ouabain-binding sites than myoblasts with an apparent dissociation constant (Kd) of 1.4 X 10(-7) M. The results indicate that muscle cells can express multiple isozymes of Na,K-ATPase and that expression of the alpha 2 isozyme is developmentally regulated during myogenesis.
...
PMID:Differential expression of the Na,K-ATPase alpha 1 and alpha 2 subunit genes in a murine myogenic cell line. Induction of the alpha 2 isozyme during myocyte differentiation. 284 80

Prednisolone-3,20-bisguanylhydrazone (PBGH), a steroid derivative, has been shown to inhibit Na+,K+-ATPase isolated from guinea-pig heart or kidney in concentrations significantly lower than those required to inhibit the enzyme obtained from other sources. Because Na+,K+-ATPases obtained from guinea-pig heart or kidney are predominantly of the alpha isoform, the hypothesis that PBGH selectively inhibits the alpha isoform over alpha (+) isoform of the enzyme was tested. Sodium dodecylsulfate polyacrylamide gel electrophoresis of the enzyme preparations revealed the presence of only the higher mobility, alpha isoform in guinea-pig heart and ferret kidney, whereas those from guinea-pig brain, dog brain and ferret heart showed both high and low mobility isoforms corresponding to alpha and alpha (+) isoforms. Na+,K+-ATPase obtained from the guinea-pig heart was most sensitive to PBGH and those isolated from ferret heart or ferret kidney had the lowest sensitivity. Enzyme preparations obtained from dog brain, dog heart or guinea-pig brain had intermediate sensitivity. This spectrum of enzyme sensitivity to PBGH was markedly different from that to ouabain. In ferret heart Na+,K+-ATPase, a low concentration of PBGH preferentially inhibited [3H]ouabain binding to the high affinity ouabain binding sites (alpha(+) isoform). These results indicate that PBGH is not a specific inhibitor of the alpha isoforms of Na+,K+-ATPase. Affinity of the enzyme for PBGH is determined by the species and tissue rather than isoforms of Na+,K+-ATPase.
...
PMID:Cardiac Na+,K+-ATPase isoenzymes: sensitivity to prednisolone bisguanylhydrazone. 285 75

Rat brain and kidney cDNA libraries were constructed and screened with a cDNA insert corresponding to the mRNA for the sheep kidney Na+,K+-ATPase catalytic subunit. The alpha-subunit cDNAs isolated from the kidney library were derived from a single class of messenger RNA, and the brain cDNAs were derived from three classes of messenger RNA. The most abundant brain cDNA, which spans 5.1 kilobases, encodes the alpha(+) form of the enzyme. The second most abundant brain cDNA, which spans 3.65 kilobases, is identical with that of the kidney form and therefore encodes the alpha isoform. The third class of cDNA, which spans 3.55 kilobases, was present at low abundance and encodes an isoform of the alpha-subunit, designated alpha III, which has not been identified previously. The complete nucleotide sequence and deduced amino acid sequence for each of the brain and kidney cDNAs have been determined. In addition, we have identified a lysine-rich sequence that may function as a movable, ion-selective gate during cation binding and occlusion and have also identified several amino acid sequence variations that appear to explain some of the well-known species and tissue differences in cardiac glycoside sensitivity.
...
PMID:Molecular cloning of three distinct forms of the Na+,K+-ATPase alpha-subunit from rat brain. 302 70

The coexpression of multiple isoforms of the alpha and beta subunits of the Na,K-ATPase in mammalian tissues gives rise to the complex molecular heterogeneity that characterizes the Na pump. The expression of the different Na,K-ATPase isoforms in insect cells using recombinant baculoviruses represents a useful system for the analysis of Na,K-ATPase isoform function. In the present study, we use this system to direct the expression of the rat Na,K-ATPase alpha 3 beta 1 and alpha 3 beta 2 in sf-9 cells, a cell line derived from the ovary of the fall armyworm, Spodoptera frugiperda. The association of alpha 3 with either beta 1 or beta 2 results in catalytically competent Na,K-ATPase isozymes. Analysis of the kinetic characteristics of these enzymes demonstrates that the accompanying beta subunit isoform does not drastically affect the properties of the alpha 3 polypeptide. This is evidenced by the similar turnover numbers, apparent affinities for K+ and ATP, and the comparable high sensitivity to ouabain exhibited by both isozymes. The kinetic dependence on Na+, however, is different for both isozymes, with alpha 3 beta 2 displaying a 1.6-fold higher apparent affinity for the cation than alpha 3 beta 1. Comparison with other Na,K-ATPase isozymes shows that the apparent Na+ affinity of alpha 3 beta 2 is similar to that of the alpha 1 beta 1 Na pump widely expressed in every tissue; nevertheless, its reactivity toward K+, ATP, and ouabain are characteristic of the alpha 3 isoform. The most pronounced kinetic differences in Na,K-ATPase function are a result of variations in alpha isoform composition.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Comparison of the enzymatic properties of the Na,K-ATPase alpha 3 beta 1 and alpha 3 beta 2 isozymes. 763 89

The Na+,K(+)-ATPase alpha subunit has three known isoforms, alpha 1, alpha 2 and alpha 3, each encoded by a separate gene. This study was undertaken to determine the functional status of a fourth human alpha-like gene, ATP1AL2. Partial genomic sequence analysis revealed regions exhibiting sequence similarity with exons 3-6 of the Na+,K(+)-ATPase alpha isoform genes. ATP1AL2 cDNAs spanning the coding sequence of a novel P-type ATPase alpha subunit were isolated from a rat testis library. The predicted polypeptide is 1028 amino acids long and exhibits 76-78% identity with the rat Na+,K(+)-ATPase alpha 1, alpha 2 and alpha 3 isoforms, indicating that ATP1AL2 may encode a fourth Na+,K(+)-ATPase alpha isoform. A 3.9-kb mRNA is expressed abundantly in human and rat testis.
...
PMID:A putative fourth Na+,K(+)-ATPase alpha-subunit gene is expressed in testis. 780 53

The Na,K-ATPase is an integral plasma membrane protein consisting of alpha and beta subunits, each of which has discrete isoforms expressed in a tissue-specific manner. Of the three functional alpha isoform genes, the one encoding the alpha 3 isoform is the most tissue-restricted in its expression, being found primarily in the brain. To identify regions of the alpha 3 isoform gene that are involved in directing expression in the brain, a 1.6 kb 5'-flanking sequence was attached to a reporter gene, chloramphenicol acetyltransferase (CAT). The alpha 3-CAT chimeric gene construct was microinjected into fertilized mouse eggs, and transgenic mice were produced. Analysis of adult transgenic mice from different lines revealed that the transgene is expressed primarily in the brain. To further delineate regions that are needed for conferring expression in this tissue, systematic deletions of the 5'-flanking sequence of the alpha 3-CAT fusion constructs were made and analyzed, again using transgenic mice. The results from these analyses indicate that DNA sequences required for mediating brain-specific expression of the alpha 3 isoform gene are present within 210 bp upstream of the transcription initiation site. alpha 3-CAT promoter constructs containing scanning mutations in this region were also assayed in transgenic mice. These studies have identified both a functional neural-restrictive silencer element as well as a positively acting cis element.
...
PMID:The presence of both negative and positive elements in the 5'-flanking sequence of the rat Na,K-ATPase alpha 3 subunit gene are required for brain expression in transgenic mice. 798 27

To characterize the expression of genes encoding the alpha- and beta-subunit isoforms of the Na(+)-K(+)-ATPase in rat kidney, we used reverse transcription (RT)-PCR of microdissected renal structures combined with quantitation of subunit isoform mRNAs in the major renal parenchymal zones. Transcripts for alpha 1, alpha 2, alpha 3, beta 1, and beta 2 subunit isoforms were detected by RT-PCR in microdissected glomeruli, proximal convoluted tubules, medullary thick ascending limbs of Henle, cortical and inner medullary collecting ducts. The truncated alpha 1 (alpha 1-T) isoform was also amplified from cortex, outer and inner medulla and isolated glomeruli, but it was not detected in these nephron segments. The DNA sequence of the renal alpha 1-T PCR product was identical to that of the cDNA previously cloned from aortic smooth muscle cells. RNA dot-blot analysis indicated that the alpha 1, alpha 2, and alpha 3 isoforms contributed approximately 70%, approximately 20%, and approximately 10%, respectively, of the total alpha isoform mRNA in each parenchymal zone. RNase protection assays determined that the beta 1 and beta 2 isoforms accounted for approximately 95% and approximately 5%, respectively, of the beta isoform mRNA in each zone. These data provide definitive evidence for the differential expression of mRNAs encoding all the alpha and beta isoforms in the renal parenchyma, and for the coexpression of these isoforms in the nephron segments examined. The results suggest the potential expression of up to eight different Na(+)-K(+)-ATPase isoenzymes in the kidney, and for multiple molecular levels of regulation of renal Na(+)-K(+)-ATPase expression.
...
PMID:Segmental localization of mRNAs encoding Na(+)-K(+)-ATPase alpha- and beta-subunit isoforms in rat kidney using RT-PCR. 799 86

In the renal cortical collecting duct (CCD), mineralocorticoid hormones, like aldosterone, augment the abundance of Na/K-ATPase molecules. It has been postulated that this response involves an isoform switch of the Na/K-ATPase catalytic subunit, alpha, as the molecular basis for the differential regulation of mineralo-corticoid-induced and constitutively expressed Na/K-ATPase pools. In opposition to this attractive hypothesis, three lines of independent evidence are presented which demonstrate that the CCD exclusively expresses the alpha 1 form despite mineralocorticoid-mediated changes in functional Na/K pump density. First, aldosterone increased [3H]ouabain binding in CCD 2.5-fold without changing the ouabain dissociation constant. Second, an electrophysiological assay for pump activity revealed that aldosterone increased maximum Na/K pump current in parallel with the change in ouabain binding without altering the apparent sodium affinity. Third, Western blot analysis with alpha isoform-specific, antipeptide antibodies demonstrated that aldosterone exclusively increased the total chemical pool of the alpha 1 form of the pump without inducing other alpha subunit isoforms. In summary, aldosterone increases the abundance of Na/K-ATPase molecules in the CCD which are pharmacologically, physiologically, and chemically indistinguishable from those that are normally expressed.
...
PMID:Aldosterone-mediated Na/K-ATPase expression is alpha 1 isoform specific in the renal cortical collecting duct. 822 73

Site-directed mutagenesis was used to examine the importance of five carboxyl-containing amino acids localized in the putative membrane-spanning regions of the Na,K-ATPase (i.e., E327, E778, D803, D807, and D925 of the rat alpha 2 isoform). The substitutions were introduced into a cDNA encoding a ouabain-resistant isoform (i.e., rat alpha 2* which was mutated to encode a ouabain-resistant isoform), and the effect of these substitutions on Na,K-ATPase function was assessed by screening the altered enzymes for their ability to confer ouabain resistance when expressed in otherwise ouabain-sensitive cells. The expression of the alpha isoform containing certain substitutions at positions 327 and 925 was able to confer ouabain resistance to HeLa cells while the expression of rat alpha 2* containing substitutions at positions 778, 803, and 807 was not. In particular, amino acids in each of these positions were substituted with leucine to evaluate the importance of the carboxyl-containing side chain. The ability of rat alpha 2* containing E327L and D925L to confer ouabain resistance to HeLa cells indicates that neither the negative charge nor the oxygen-containing side chain is absolutely essential for overall function in this position. In contrast, the inability of rat alpha 2* carrying E778L, D803L, and D807L to confer ouabain resistance suggests that the naturally occurring amino acid may be more critical structurally and/or functionally for the Na,K-ATPase. Other more conservative substitutions introduced to further characterize the role of particular amino acid side chains include E327D, E327Q, D803N, D803E, and D925N.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Site-directed mutagenesis of the Na,K-ATPase: consequences of substitutions of negatively-charged amino acids localized in the transmembrane domains. 825 87

To determine if an altered expression of the Na,K-ATPase alpha isoform genes is responsible for an observed increase in cardiac glycoside sensitivity in compensatory hypertrophy, we performed Northern and slot blot analyses of RNA and specific immunological detection of Na,K-ATPase isoforms in rat hearts from normal and pressure overload-treated animals induced by abdominal aortic constriction. During the early phase of hypertrophy, the only alteration is a decrease in the alpha 2 mRNA isoform. In the compensated hypertrophied heart, the levels of the predominant alpha 1 isoform (mRNA and protein) and the beta 1 subunit mRNA are unchanged. In contrast, the alpha 2 isoform (mRNA and protein) is decreased by 35% and up to 61-64% in mild (< 55%) and severe (> 55%) hypertrophy, respectively. The alpha 3 isoform (mRNA and protein), which is extremely low in adult heart, is increased up to 2-fold during hypertrophy but accounts for only approximately equal to 5% of the total alpha isoform mRNA. These findings demonstrate that, in cardiac hypertrophy, the three alpha isoforms of the Na,K-ATPase are independently regulated and that regulation occurs at a pretranslational level. The pattern of expression in hypertrophied adult heart is similar to that of the neonatal heart where the inverse regulation between the alpha 2 and alpha 3 ouabain high affinity isoforms has been reported. This suggests that distinct regulatory mechanisms controlling Na,K-ATPase isoform expression may, at least in part, be involved in the sensitivity to cardiac glycosides.
...
PMID:Alteration of Na,K-ATPase subunit mRNA and protein levels in hypertrophied rat heart. 828 20


<< Previous 1 2 3 4 5 6 Next >>

---