151
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Chalaka S, Ingbar DH, Sharma R, Zhau Z, Wendt CH. Na(+)-K(+)-ATPase gene regulation by glucocorticoids in a fetal lung epithelial cell line. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:L197-203. [PMID: 10409248 DOI: 10.1152/ajplung.1999.277.1.l197] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Na(+) pump, Na(+)-K(+)-ATPase, along with the Na(+) channel is essential for the removal of alveolar solute and fluid perinatally. Because Na(+)-pump mRNA and activity increase before birth and maternal glucocorticoids (GCs) influence Na(+)-K(+)-ATPase mRNA expression in fetal rat lung, we hypothesized that GCs increased Na(+)-K(+)-ATPase gene expression in a fetal lung epithelial cell line. After 24 h of exposure, dexamethasone increased the steady-state levels of Na(+)-K(+)-ATPase alpha(1) and beta(1) mRNA in a fetal rat lung epithelial cell line in a dose-dependent fashion (10(-7) to 10(-5) M). The maximal increase in mRNA levels was 3. 8-fold for alpha(1) and 2.8-fold for beta(1). The increase in mRNA was detected as early as 6 h for the beta(1)-subunit and 18 h for the alpha(1)-subunit, and both peaked at 24 h. This gene upregulation was not due to increased mRNA stability based on mRNA half-life determination after actinomycin D inhibition. Transfection experiments with alpha(1) and beta(1) promoter-reporter constructs demonstrated 3.2 +/- 0.5- and 2.6 +/- 0.4-fold increases, respectively, in promoter activity, consistent with transcriptional activation of the promoter-reporter construct. These findings, increased promoter activity with no change in stability, indicate that GCs increased Na(+)-K(+)-ATPase transcription in a fetal lung epithelial cell line.
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Affiliation(s)
- S Chalaka
- Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455, USA
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152
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Abstract
Novel strategies in the treatment of heart failure include mechanical unloading with a left ventricular assist device. Although first considered as a bridge to cardiac transplantation, this surgical treatment may improve cardiac function in patients with heart failure, even after removal of the device. The molecular adaptation of the heart to unloading remains largely unknown. Most of the enzymes involved in the regulation of myocardial energetics (including contractile proteins, ion pumps, and metabolic enzymes)exist in "fetal" and "adult" isoforms. It is known that cardiac hypertrophy due to increased work load in vivo involves a switching from the normally expressed adult isoform to the fetal isoform. Our work has now shown that the same pattern occurs in the unloaded heart. In both conditions, this switching is accompanied by the reexpression of growth factors and proto-oncogenes. The functional improvement of the failing heart after mechanical unloading may in part be the result of a reexpression of fetal genes.
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Affiliation(s)
- C Depre
- Department of Integrative Biology, University of Texas Houston Medical School 77030, USA
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153
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Davoli R, Zambonelli P, Bigi D, Fontanesi L, Russo V. Analysis of expressed sequence tags of porcine skeletal muscle. Gene 1999; 233:181-8. [PMID: 10375634 DOI: 10.1016/s0378-1119(99)00141-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Porcine skeletal muscle genes play a major role in determining muscle growth and meat quality. Therefore, to progress towards a better understanding of the genetic factors influencing these traits, the first step is to characterize the genes expressed in skeletal muscle tissue in pig. To this aim, we constructed a porcine biceps femoris muscle cDNA library and sequenced 111 randomly isolated clones. By FASTA analysis, we identified 72 unique clones: 47 showed homology to previously identified genes in human or other mammals, 20 matched uncharacterized expressed sequence tags (ESTs), two showed no significant matches to sequences already present in DNA databases, and three other clones containing only repetitive elements were excluded from further analysis. Mitochondrial genes (16.2%), myosin heavy chain genes (9%) and the actin alpha skeletal muscle gene (9%) were the most abundant transcripts. Among the 47 identified genes several muscle-specific or predominant sequences expressed in skeletal muscle were found. The sequences of the clones matching uncharacterized human, mouse or porcine ESTs were tested by GRAIL in order to identify putative coding regions. The results of our analysis allowed the establishment of a first list of genes expressed in porcine skeletal muscle.
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Affiliation(s)
- R Davoli
- DIPROVAL, Sezione di Allevamenti Zootecnici, University of Bologna, Via F.lli Rosselli 107, Coviolo, 42100 Reggio Emilia, Italy.
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154
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Deane EE, Kelly SP, Woo NY. Hormonal modulation of branchial Na+-K+-ATPase subunit mRNA in a marine teleost Sparus sarba. Life Sci 1999; 64:1819-29. [PMID: 10350356 DOI: 10.1016/s0024-3205(99)00124-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The effect of hormone treatment on the abundance of Na+-K+-ATPase alpha- and beta-subunit mRNA in Sparus sarba branchial tissue was investigated. Groups of seawater (33/1000) and hypo-osmotic (6/1000) acclimated fish were injected daily, with either saline, cortisol, recombinant bream growth hormone (rbGH) or ovine prolactin (oPRL). Total RNA from branchial tissue was analyzed by Northern blotting using PCR amplified Na+-K+-ATPase alpha- and beta-subunit cDNA clones. Na+-K+-ATPase alpha- and beta- subunit transcripts of 3.3kb and 2.4kb respectively, were detected and their abundance, after hormone treatment was assessed using RNA dot blots. The abundance of subunit mRNAs increased 1.4-1.9 fold, relative to controls, after cortisol treatment. The alpha:beta mRNA ratio also increased in cortisol treated seawater acclimated fish. Growth hormone treatment did not cause any significant changes in Na+-K+-ATPase subunit mRNA, whereas prolactin significantly reduced alpha-subunit mRNA levels by approximately 0.5 fold in both seawater and hypo-osmotic conditions. The data from this study add further support to the generally accepted roles that cortisol and prolactin have in the modulation of Na+-K+-ATPase activity. It can be concluded from this study that S. sarba branchial Na+-K+-ATPase subunit expression is multihormonally regulated.
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Affiliation(s)
- E E Deane
- Department of Biology, The Chinese University of Hong Kong, NT, China
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155
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Petershack JA, Nagaraja SC, Guillery EN. Role of glucocorticoids in the maturation of renal cortical Na+-K+-ATPase during fetal life in sheep. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:R1825-32. [PMID: 10362766 DOI: 10.1152/ajpregu.1999.276.6.r1825] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucocorticoid levels increase greatly at the time of birth in humans and sheep, coinciding with an increased ability of the kidney to reabsorb sodium. Cortisol induces proximal tubule apical membrane Na+/H+ exchanger maturation in near-term fetal sheep. Proximal tubule salt transport is ultimately dependent on Na+ pump activity, so we studied the effects of cortisol treatment on renal cortical Na+-K+-ATPase. We first looked at six 140 day gestation fetal sheep (term is 145) and compared their renal cortical Na+-K+-ATPase to that of six 1-day-old lambs. Na+-K+-ATPase activity increased 80% after birth. Then nine pairs of twin fetal sheep were chronically instrumented at 127 days gestation. After 72 h recovery, one twin was given a 48-h continuous intraperitoneal infusion of cortisol. Both twins were then killed, and their renal cortices were studied. Na+-K+-ATPase activity increased 122% with cortisol treatment; activity equaled that of 1-day-old lambs. Protein abundance of the alpha1-subunit of the Na+-K+-ATPase increased 19%; the beta1-subunit increased 39% with cortisol treatment. mRNA abundance of the alpha1-subunit increased 58%; the beta1-subunit increased 72%. These results indicate that cortisol matures Na+-K+-ATPase activity.
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Affiliation(s)
- J A Petershack
- Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, Michigan 48197, USA.
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156
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Thompson CB, Choi C, Youn JH, McDonough AA. Temporal responses of oxidative vs. glycolytic skeletal muscles to K+ deprivation: Na+ pumps and cell cations. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 276:C1411-9. [PMID: 10362605 DOI: 10.1152/ajpcell.1999.276.6.c1411] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
When K+ output exceeds input, skeletal muscle releases intracellular fluid K+ to buffer the fall in extracellular fluid (ECF) K+. To investigate the mechanisms and muscle specificity of the K+ shift, rats were fed K+-deficient chow for 2-10 days, and two muscles at phenotypic extremes were studied: slow-twitch oxidative soleus and fast-twitch glycolytic white gastrocnemius (WG). After 2 days of low-K+ chow, plasma K+ concentration ([K+]) fell from 4.6 to 3.7 mM, and Na+-K+-ATPase alpha2 (not alpha1) protein levels in both muscles, measured by immunoblotting, decreased 36%. Cell [K+] decreased from 116 to 106 mM in soleus and insignificantly in WG, indicating that alpha2 can decrease before cell [K+]. After 5 days, there were further decreases in alpha2 (70%) and beta2 (22%) in WG, not in soleus, whereas cell [K+] decreased and cell [Na+] increased by 10 mM in both muscles. By 10 days, plasma [K+] fell to 2.9 mM, with further decreases in WG alpha2 (94%) and beta2 (70%); cell [K+] fell 19 mM in soleus and 24 mM in WG compared with the control, and cell [Na+] increased 9 mM in soleus and 15 mM in WG; total homogenate Na+-K+-ATPase activity decreased 19% in WG and insignificantly in soleus. Levels of alpha2, beta1, and beta2 mRNA were unchanged over 10 days. The ratios of alpha2 to alpha1 protein levels in both control muscles were found to be nearly 1 by using the relative changes in alpha-isoforms vs. beta1- (soleus) or beta2-isoforms (WG). We conclude that the patterns of regulation of Na+ pump isoforms in oxidative and glycolytic muscles during K+ deprivation mediated by posttranscriptional regulation of alpha2beta1 and alpha2beta2 are distinct and that decreases in alpha2-isoform pools can occur early enough in both muscles to account for the shift of K+ to the ECF.
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Affiliation(s)
- C B Thompson
- Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles, California 90033, USA
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157
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Pribnow D, Johnson-Pais T, Bond CT, Keen J, Johnson RA, Janowsky A, Silvia C, Thayer M, Maylie J, Adelman JP. Skeletal muscle and small-conductance calcium-activated potassium channels. Muscle Nerve 1999; 22:742-50. [PMID: 10366228 DOI: 10.1002/(sici)1097-4598(199906)22:6<742::aid-mus11>3.0.co;2-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Skeletal muscle becomes hyperexcitable following denervation and when cultured in the absence of nerve cells. In these circumstances, the bee venom peptide toxin apamin, a blocker of small-conductance calcium-activated potassium (SK) channels, dramatically reduces the hyperexcitability. In this report, we show that SK3 channels are expressed in denervated skeletal muscle and in L6 cells. Action potentials evoked from normal innervated rat skeletal muscle did not exhibit an afterhyperpolarization, indicating a lack of SK channel activity; very low levels of apamin binding sites, SK3 protein, or SK3 mRNA were present. However, denervation resulted in apamin-sensitive afterhyperpolarizations and increased apamin binding sites, SK3 protein, and SK3 mRNA. Cultured rat L6 myoblasts and differentiated L6 myotubes contained similar levels of SK3 mRNA, although apamin-sensitive SK currents and apamin binding sites were detected only following myotube differentiation. Therefore, different molecular mechanisms govern SK3 expression levels in denervated muscle compared with muscle cells differentiated in culture.
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Affiliation(s)
- D Pribnow
- Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, USA
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158
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James PF, Grupp IL, Grupp G, Woo AL, Askew GR, Croyle ML, Walsh RA, Lingrel JB. Identification of a specific role for the Na,K-ATPase alpha 2 isoform as a regulator of calcium in the heart. Mol Cell 1999; 3:555-63. [PMID: 10360172 DOI: 10.1016/s1097-2765(00)80349-4] [Citation(s) in RCA: 277] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
It is well accepted that inhibition of the Na,K-ATPase in the heart, through effects on the Na/Ca exchanger, raises the intracellular Ca2+ concentration and strengthens cardiac contraction. However, the contribution that individual isoforms make to this calcium regulatory role is unknown. Assessing the phenotypes of mouse hearts with genetically reduced levels of Na,K-ATPase alpha 1 or alpha 2 isoforms clearly demonstrates different functional roles for these isoforms in vivo. Heterozygous alpha 2 hearts are hypercontractile as a result of increased calcium transients during the contractile cycle. In contrast, heterozygous alpha 1 hearts are hypocontractile. The different functional roles of these two isoforms are further demonstrated since inhibition of the alpha 2 isoform with ouabain increases the contractility of heterozygous alpha 1 hearts. These results definitively illustrate a specific role for the alpha 2 Na,K-ATPase isoform in Ca2+ signaling during cardiac contraction.
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Affiliation(s)
- P F James
- Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, Ohio 45267, USA
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159
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Fontanesi L, Davoli R, Zijlstra C, Bosma AA, Russo V. Mapping of the Na+, K(+)-ATPase subunit alpha 2 (ATP1A2) and muscle phosphofructokinase (PFKM) genes in pig by somatic cell hybrid analysis. Anim Genet 1999; 30:57-9. [PMID: 10050286 DOI: 10.1046/j.1365-2052.1999.00407.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Two expressed sequence tags were isolated from a porcine skeletal muscle cDNA library and identified as the putative partial cDNAs of the porcine Na+, K(+)-ATPase subunit alpha 2 (ATP1A2) and muscle phosphofructokinase (PFKM) genes after sequencing and homology search. Results of analysis of a pig-rodent somatic cell hybrid panel by PCR allowed the assignments of ATP1A2 to porcine chromosome (chr) 4 and of PFKM to porcine chr 5. These assignments support previously observed conservation of syntenic relationships between human chr 1 and porcine chr 4 and between human chr 12 and porcine chr 5.
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Affiliation(s)
- L Fontanesi
- DIPROVAL-Sezione di Allevamenti Zootecnici, Faculty of Agriculture, University of Bologna, Reggio Emilia, Italy
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160
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Yalcin Y, Carman D, Shao Y, Ismail-Beigi F, Klein I, Ojamaa K. Regulation of Na/K-ATPase gene expression by thyroid hormone and hyperkalemia in the heart. Thyroid 1999; 9:53-9. [PMID: 10037077 DOI: 10.1089/thy.1999.9.53] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Hypothermic hyperkalemic circulatory arrest has been widely used for myocardial protection during heart surgery. Recent data showed that administration of triiodo-L-thyronine (T3) postoperatively enhanced ventricular function. The effect of hyperkalemic arrest in conjunction with thyroid hormone on the plasma membrane enzyme sodium/potassium-adenosine triphosphatase (Na/K-ATPase), was determined in cultured neonatal rat atrial and ventricular myocytes. Exposure of ventricular myocytes to hyperkalemic medium (50 mM KCl) in the absence of T3 increased expression of the Na/K-ATPase catalytic subunit mRNAs, alpha1 and alpha3 isoforms, by 1.9- and 1.5-fold, respectively (p<0.01), which were accompanied by similar increases (1.4- and 1.8-fold) in protein content. Addition of T3 to the hyperkalemic cultures attenuated these increases in Na/K-ATPase mRNA isoforms to levels of expression observed in cells treated with T3 (10(-8) M) alone. Similarly, expression of the alpha1 mRNA isoform in atrial myocytes was increased (p<0.05) by hyperkalemic conditions, and T3 treatment attenuated this effect. In contrast, although expression of the Na/K-ATPase beta1 mRNA in both atrial and ventricular myocytes was significantly increased by hyperkalemia, addition of T3 did not prevent the hyperkalemic response, and in atrial myocytes T3 significantly increased beta1 mRNA expression 1.8-fold. These results show that expression of cardiac Na/K-ATPase is regulated by T3 and hyperkalemia in an isoform and chamber specific manner, and suggest that use of hyperkalemic cardioplegia during heart surgery may alter plasma membrane ion function.
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Affiliation(s)
- Y Yalcin
- Department of Pediatrics, North Shore University Hospital, NYU School of Medicine, Manhasset, New York 11030, USA
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161
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Ogawa T, Linz W, Schölkens BA, de Bold AJ. Regulation of aortic atrial natriuretic factor and angiotensinogen in experimental hypertension. J Cardiovasc Pharmacol 1998; 32:1001-8. [PMID: 9869508 DOI: 10.1097/00005344-199812000-00019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We investigated the relation between atrial natriuretic factor (ANF) gene expression and the status of the renin-angiotensin system (RAS) in aortic tissue in rats made hypertensive by either aortic banding or by deoxycorticosterone acetate (DOCA)-salt administration. These experimental models of hypertension are known to have differences in terms of the status of RAS. ANF messenger RNA (mRNA) levels were measured in aortic tissue by using a newly developed quantitative competitive reverse transcription polymerase chain reaction (QC-RT-PCR) technique. Changes in the proportions of alpha1 and alpha2 isoforms of Na+K+-adenosine triphosphatase (ATPase) mRNA levels were used as indicators of aortic hypertrophy. Treatment with DOCA alone, salt alone, or DOCA-salt for 5 weeks increased aortic-weight/body-weight ratio and aortic angiotensinogen mRNA levels, but did not change alpha1 or alpha2 Na+K+-ATPase mRNA levels. Aortic ANF mRNA levels had a tendency to increase after treatment with DOCA, salt, or DOCA-salt, but this change did not reach statistical significance. Suprarenal aortic banding for 6 weeks or 12 weeks increased aortic-weight/body-weight ratio (12 weeks), decreased alpha2 Na+K+-ATPase and angiotensinogen mRNA levels, but did not affect alpha1 Na+K+-ATPase mRNA levels or ANF mRNA levels. Treatment with ramipril, an angiotensin-converting enzyme (ACE) inhibitor was carried out for 6 weeks just after aortic banding (prevention experiment) or after 6 weeks in rats that were banded for the previous 6 weeks (regression experiment). High-dose ramipril (1 mg/kg)--a treatment known to inhibit both tissue and circulating RAS--normalized aortic-weight/body-weight ratio, and also normalized alpha2 Na+K+-ATPase mRNA levels. Aortic angiotensinogen mRNA levels of banded rats treated with high-dose ramipril was higher than those of the normal control, sham operated, and banded rats. Treatment with high-dose ramipril did not affect alpha1 Na+K+-ATPase mRNA levels or ANF mRNA levels. Low-dose ramipril (10 microg/kg)--a treatment that selectively inhibits tissue RAS--normalized aortic-weight/body-weight ratio but did not normalize alpha2 Na+K+-ATPase mRNA levels (regression experiment) or angiotensinogen mRNA levels (prevention experiment) and did not change either alpha1 Na+K+-ATPase mRNA levels or ANF mRNA levels. The results suggest that, in contrast to previous findings in heart and kidney, the regulation of ANF mRNA levels in aortic tissue is largely independent of pressure load, volume load, and plasma or tissue RAS. It is suggested that any antihypertrophic actions of ANF may be mediated by the increased circulating ANF levels and its interaction with its receptor or through CNP.
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Affiliation(s)
- T Ogawa
- University of Ottawa Heart Institute at the Ottawa Hospital, Ontario, Canada
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162
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Blanco G, Sánchez G, Mercer RW. Differential regulation of Na,K-ATPase isozymes by protein kinases and arachidonic acid. Arch Biochem Biophys 1998; 359:139-50. [PMID: 9808755 DOI: 10.1006/abbi.1998.0904] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
While several studies have investigated the regulation of the Na, K-ATPase consisting of the alpha1 and beta1 subunits, there is little evidence that intracellular messengers influence the other Na pump isozymes. We studied the effect of different protein kinases and arachidonic acid on the rat Na,K-ATPase isoforms expressed in Sf-9 insect cells. Our results indicate that PKA, PKC, and PKG are able to differentially modify the function of the Na,K-ATPase isozymes. While PKC activation leads to inhibition of all isozymes, PKA activation stimulates the activity of the Na,K-ATPase alpha3 beta1 and decreases that of the alpha1 beta1 and alpha2 beta1 isozymes. In contrast, activation of PKG diminishes the activity of the alpha1 beta1 and alpha3 beta1 isozymes, without altering that of alpha2 beta1. Treatment of cells with arachidonic acid reduced the activities of all the isozymes. The changes in the catalytic capabilities of the Na pump isozymes elicited by PKA and PKC are reflected by changes in the molecular activity of the Na,K-ATPases. One of the mechanisms by which PKA and PKC affect Na pump isozyme activity is through direct phosphorylation of the alpha subunit. In the insect cells, we found a PKA- and PKC-dependent phosphorylation of the alpha1, alpha2 and alpha3 polypeptides. In conclusion, several intracellular messengers are able to modulate the function of the Na,K-ATPase isozymes and some of them in a specific fashion. Because the Na,K-ATPase isozymes have kinetic properties that are unique, this isozyme-specific regulation may be important in adapting Na pump function to the requirements of each cell.
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Affiliation(s)
- G Blanco
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA
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163
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Blanco G, Mercer RW. Isozymes of the Na-K-ATPase: heterogeneity in structure, diversity in function. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:F633-50. [PMID: 9815123 DOI: 10.1152/ajprenal.1998.275.5.f633] [Citation(s) in RCA: 576] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Na-K-ATPase is characterized by a complex molecular heterogeneity that results from the expression and differential association of multiple isoforms of both its alpha- and beta-subunits. At present, as many as four different alpha-polypeptides (alpha1, alpha2, alpha3, and alpha4) and three distinct beta-isoforms (beta1, beta2, and beta3) have been identified in mammalian cells. The stringent constraints on the structure of the Na pump isozymes during evolution and their tissue-specific and developmental pattern of expression suggests that the different Na-K-ATPases have evolved distinct properties to respond to cellular requirements. This review focuses on the functional properties, regulation, and possible physiological relevance of the Na pump isozymes. The coexistence of multiple alpha- and beta-isoforms in most cells has hindered the understanding of the roles of the individual polypeptides. The use of heterologous expression systems has helped circumvent this problem. The kinetic characteristics of different Na-K-ATPase isozymes to the activating cations (Na+ and K+), the substrate ATP, and the inhibitors Ca2+ and ouabain demonstrate that each isoform has distinct properties. In addition, intracellular messengers differentially regulate the activity of the individual Na-K-ATPase isozymes. Thus the regulation of specific Na pump isozymes gives cells the ability to precisely coordinate Na-K-ATPase activity to their physiological requirements.
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Affiliation(s)
- G Blanco
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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164
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Erichsen S, Stierna P, Bagger-Sjöbäck D, Curtis LM, Rarey KE, Schmid W, Hultcrantz M. Distribution of Na,K-ATPase is normal in the inner ear of a mouse with a null mutation of the glucocorticoid receptor. Hear Res 1998; 124:146-54. [PMID: 9822912 DOI: 10.1016/s0378-5955(98)00117-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
This study was performed in order to test the hypothesis that the glucocorticoid hormone stimulates the formation of Na,K-ATPase in the inner ear of the mouse. An immunohistochemical study with respect to the presence and distribution of glucocorticoid receptors (GR) and Na,K-ATPase in the vestibular and cochlear regions of the inner ear was performed on a C57BL mouse with a null mutation of the glucocorticoid receptor (GR mutant mouse). The wild type C57BL mouse and the CBA mouse served as normal controls. As expected, the homozygous GR mutant mouse showed no specific staining for GR in the inner ear. The heterozygous GR mutant mouse showed faint staining of GR in the spiral limbus, the spiral ganglion, the organ of Corti and the utricle. This staining was markedly less than in the wild type C57BL mouse. Antibody labelling of Na,K-ATPase in the inner ear showed no significant difference between the homozygous and the heterozygous GR mutant mouse as compared to the control wild type C57BL mouse or the CBA mouse. Although earlier studies have shown a positive correlation between levels of glucocorticoid hormone in serum and the concentration of Na,K-ATPase in the inner ear, the hypothesis that glucocorticoid hormones alone stimulate the formation of Na,K-ATPase in the inner ear could not be confirmed by this study. Thus other regulating substances must be considered.
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Affiliation(s)
- S Erichsen
- Department of Otorhinolaryngology, Karolinska Hospital, Stockholm, Sweden
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165
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Muto S, Nemoto J, Ebata S, Kawakami K, Asano Y. Corticosterone and 11-dehydrocorticosterone stimulate Na,K-ATPase gene expression in vascular smooth muscle cells. Kidney Int 1998; 54:492-508. [PMID: 9690216 DOI: 10.1046/j.1523-1755.1998.00033.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND In mineralocorticoid target tissues such as kidney and colon, the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta OHSD) catalizes the reversible conversion of corticosterone (CS) to inactive 11-dehydrocorticosterone (DHCS) in rats, and cortisol to inactive cortisone in humans. This enzyme is also expressed in vascular smooth muscle cells (VSMC). METHODS In cultured VSMC from rat thoracic aortae, we examined the effects of CS and DHCS on Na,K-ATPase alpha 1- and beta 1-mRNA accumulation by Northern blot analysis, on alpha 1- and beta 1-subunit protein accumulation by Western blot analysis, and on Na,K-ATPase activity by the coupled assay method. RESULTS In VSMC, CS and DHCS (10(-6) M) increased alpha 1-mRNA level 2.6- and 2.5-fold at 48 hours and beta 1-mRNA level 9.2- and 9.1-fold at 12 hours, respectively. The RNA transcription inhibitor (actinomycin D) abolished both CS- and DHCS-mediated alpha 1- and beta 1-mRNA induction. The glucocorticoid receptor antagonist (RU38486) and the mineralocorticoid receptor antagonists (ZK91587) inhibited both CS- and DHCS-mediated alpha 1- and beta 1-mRNA induction. The 11 beta OHSD inhibitor (carbenoxolone) inhibited DHCS-mediated alpha 1- and beta 1-mRNA induction, whereas it caused no effect on CS-mediated alpha 1- or beta 1-mRNA induction. The addition of CS or DHCS to VSMC significantly increased alpha 1- and beta 1-subunit protein levels and Na,K-ATPase activity. When adrenalectomized rats were treated with CS or DHCS for 12 hours, aorta alpha 1- and beta 1-mRNA levels increased 3.0- and 8.7-fold or 3.4- and 8.4-fold, respectively. CONCLUSIONS In VSMC, both CS and DHCS stimulate Na,K-ATPase alpha 1- and beta 1-mRNA accumulation, alpha 1- and beta 1-subunit protein accumulation, and Na,K-ATPase activity. The CS-mediated alpha 1- and beta 1-mRNA induction occurs independently of 11 beta OHSD, whereas the DHCS-mediated alpha 1- and beta 1-mRNA induction occurs through 11 beta OHSD-dependent mechanisms, possibly via conversion of inactive DHCS into active CS.
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Affiliation(s)
- S Muto
- Department of Nephrology, Jichi Medical School, Tochigi, Japan
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166
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Minakata Y, Suzuki S, Grygorczyk C, Dagenais A, Berthiaume Y. Impact of beta-adrenergic agonist on Na+ channel and Na+-K+-ATPase expression in alveolar type II cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:L414-22. [PMID: 9700104 DOI: 10.1152/ajplung.1998.275.2.l414] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
It has been shown that short-term (hours) treatment with beta-adrenergic agonists can stimulate lung liquid clearance via augmented Na+ transport across alveolar epithelial cells. This increase in Na+ transport with short-term beta-agonist treatment has been explained by activation of the Na+ channel or Na+-K+-ATPase by cAMP. However, because the effect of sustained stimulation (days) with beta-adrenergic agonists on the Na+ transport mechanism is unknown, we examined this question in cultured rat alveolar type II cells. Na+-K+-ATPase activity was increased in these cells by 10(-4) M terbutaline in an exposure time-dependent manner over 7 days in culture. This increased activity was also associated with an elevation in transepithelial current that was inhibited by amiloride. The enzyme's activity was also augmented by continuous treatment with dibutyryl-cAMP (DBcAMP) for 5 days. This increase in Na+-K+-ATPase activity by 10(-4) M terbutaline was associated with an increased expression of alpha1-Na+-K+-ATPase mRNA and protein. beta-Adrenergic agonist treatment also enhanced the expression of the alpha-subunit of the epithelial Na+ channel (ENaC). These increases in gene expression were inhibited by propranolol. Amiloride also suppressed this long-term effect of terbutaline and DBcAMP on Na+-K+-ATPase activity. In conclusion, beta-adrenergic agonists enhance the gene expression of Na+-K+-ATPase, which results in an increased quantity and activity of the enzyme. This heightened expression is also associated with augmented ENaC expression. Although the cAMP system is involved, the inhibition of enhanced enzyme activity with amiloride suggests that increased Na+ entry at the apical surface plays a role in this process.
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Affiliation(s)
- Y Minakata
- Centre de Recherche, Centre Hospitalier de l'Université de Montréal, Montreal, Quebec H2W 1T8, Canada
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167
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Chang CS, Kirk RG, Lee P. Presence of immunoreactive alpha 3 subunit isoform of Na,K-ATPase in mitochondria of kidney. Kidney Int 1998; 54:457-63. [PMID: 9690212 DOI: 10.1046/j.1523-1755.1998.00031.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Sodium-potassium-adenosinetriphosphatase (Na,K-ATPase) is the primary membrane enzyme responsible for the reabsorption of sodium ions in the kidney. It is known that in the nephron the major subunit isoforms of Na,K-ATPase are alpha 1 and beta 1. Previous reports on the presence of alpha 2 and alpha 3 isoforms in the kidney were mixed and controversial. METHODS Techniques of ultrathin cryosectioning and immunoelectron microscopy were used to study the distribution of alpha subunit isoforms (alpha 1, alpha 2, alpha 3) and beta subunit (beta 1 isoform) of Na,K-ATPase in renal tubular cells. Western blot analysis was used to show the presence of the alpha 3 isoform in the extract of kidney mitochondria. RESULTS We were able to confirm the previous finding that the alpha 1 isoform and the beta 1 isoform were the preponderant isoforms of the alpha and beta subunits of Na,K-ATPase in the basolateral membrane. In addition, we unexpectedly found the presence of the alpha 3 isoform in the mitochondria of rat renal tubular cells. The alpha 2 and alpha 3 isoforms were not observed in either the apical or basolateral membrane. CONCLUSIONS Both immunoelectron microscopy and Western blot analysis of the rat kidney mitochondria confirm the presence of the alpha 3 isoform of Na,K-ATPase in the rat kidney mitochondria. The function of this enzyme in the mitochondria is not clear at this time.
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Affiliation(s)
- C S Chang
- Department of Physiology, Robert C. Byrd Health Sciences Center, West Virginia University, Morgantown, USA
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168
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Vásárhelyi B, Vér A, Nobilis A, Szabó T, Tulassay T. Functional and structural properties of Na+/K(+)-ATPase enzyme in neonatal erythrocytes. Eur J Clin Invest 1998; 28:543-5. [PMID: 9726034 DOI: 10.1046/j.1365-2362.1998.00337.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The Na+/K(+)-pump is the main regulator enzyme of intracellular monovalent cation concentration. There are only limited data available concerning its structure and function in healthy neonates, in comparison with data available regarding its structure and function in children. PATIENTS AND METHODS Samples of 100 microL of anticoagulated blood were taken from 53 healthy neonates (age under 6th postnatal day, median age 3.5 days) and 61 healthy children (median age 12.4 months, range 6-36 months,). The Na+/K(+)-ATPase activity, its sensitivity to ouabain (a digoxin-analogue substance) and the expression of Na+/K(+) ATPase subunit isoforms were determined. RESULTS The enzyme activity (429.2 +/- 17.2 versus 295.5 +/- 10.2 U, P < 0 x 0.001) and I50 value for ouabain inhibition (1.50 +/- 0.10 versus 0.96 +/- 0.10 mumol L-1, P < 0.05) was higher in neonates. More alpha 1 subunits (relative density: 1.16 +/- 0.10 versus 0.75 +/- 0.03, P < 0.001) and higher alpha 1/ alpha 2 ratio (4.14 +/- 0.21 versus 2.02 +/- 0.16, P < 0.01) were detected. CONCLUSION This is the first study demonstrating changes of Na+/K(+) -ATPase molecules not only in enzyme activity, but also on protein level. Our results might contribute to the understanding of the resistance of neonatal cell membranes toward the pharmacodynamic actions of cardiac glycosides.
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Affiliation(s)
- B Vásárhelyi
- Semmelweis Medical University, Budapest, Hungary
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169
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Ruddy MK, Drazen JM, Pitkanen OM, Rafii B, O'Brodovich HM, Harris HW. Modulation of aquaporin 4 and the amiloride-inhibitable sodium channel in perinatal rat lung epithelial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:L1066-72. [PMID: 9609747 DOI: 10.1152/ajplung.1998.274.6.l1066] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
During the perinatal period, a dramatic reversal of lung transepithelial ion and water transport occurs that involves the amiloride-inhibitable Na+ channel (ENaC). Aquaporin (AQP) water channel proteins facilitate cell membrane water transport. We now report that AQP-4, localized to basolateral membranes of airway epithelial cells, increases its mRNA expression in developing lung eightfold during the 2 days before birth to reach a peak on the first postnatal day in the lungs but not in brains or kidneys of neonatal rats. AQP-4 and the alpha-, beta-, and gamma-subunits of ENaC are both expressed by cultured rat fetal distal lung epithelial (FDLE) cells. AQP-4 and ENaC expression increase in FDLE cells cultured on uncoated permeant filters compared with matched control cells cultured on filters containing extracellular matrix derived from fetal lung epithelial cells. Similarly, AQP-4 expression increases in FDLE cells exposed to 21% O2 compared with cells exposed to 3% O2. These data demonstrate that AQP-4 expression is highest on the first day after birth in neonatal rat lungs. Exposure to ambient 21% O2 may contribute to increases in AQP-4 and ENaC expression to facilitate water transport across neonatal airway epithelia in the immediate postnatal period.
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Affiliation(s)
- M K Ruddy
- Division of Respiratory Diseases, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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170
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Ramírez-Gil JF, Trouvé P, Mougenot N, Carayon A, Lechat P, Charlemagne D. Modifications of myocardial Na+,K(+)-ATPase isoforms and Na+/Ca2+ exchanger in aldosterone/salt-induced hypertension in guinea pigs. Cardiovasc Res 1998; 38:451-62. [PMID: 9709406 DOI: 10.1016/s0008-6363(98)00007-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
OBJECTIVE The aim of this study was to determine whether changes in cardiac Na+,K(+)-ATPase subunits and Na+/Ca2+ exchanger expression are regulated in aldosterone-salt hypertensive guinea pigs. METHODS Guinea pigs (GP) were unilaterally nephrectomized and randomized into three groups (aldosterone-salt; control-salt; control). After 90 days of treatment, echocardiographic M-mode assessment and right carotid arterial catheterization were performed in vivo, and plasma hormones and electrolytes were measured. mRNA and protein levels were studied by Northern and Western blot analysis. RESULTS Aldosterone-salt treatment induced, (1) arterial hypertension (+40%) and LV hypertrophy (+60%) without altering LV-fractional shortening, (2) an increase in plasma norepinephrine levels (+262%) and suppression of renin activity. Northern blot analysis showed the presence of the mRNA encoding the three alpha isoforms and the beta 1 subunit of Na+,K(+)-ATPase in GP myocardium. In the aldosterone-salt group, levels of alpha 1 and beta 1 mRNAs were unchanged. alpha 2 mRNA was increased in both ventricles, whereas alpha 3 mRNA was increased in hypertrophied LV only. Furthermore, levels of the Na+/Ca2+ exchanger mRNA were decreased in both ventricles. At protein level, the two major transcripts (alpha 1 and alpha 2) were detected but alpha 3 isoform was not. Parallel changes in protein and mRNA accumulation of alpha 1 and alpha 2 isoforms were observed in hypertrophied LV. CONCLUSION These results show that alpha 1 and alpha 2 isoforms are expressed in GP heart and that they are independently regulated in aldosterone-salt hypertension. Like the alpha 1 isoform in renal tissue, alpha 2 isoform is the main target of aldosterone-salt. Reciprocal expression of the Na+/Ca2+ exchanger and Na+,K(+)-ATPase suggests an adaptational mechanism which maintains an appropriate sodium gradient and calcium concentration in hypertensive myocardium.
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Affiliation(s)
- J F Ramírez-Gil
- Laboratoire de Pharmacologie Cardiovasculaire, Service de Pharmacologie, IFR Génétique et Physiopathologie Cardiovasculaire, Hôpital Pitié-Salpêtrière, Paris, France
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171
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Calviño MA, Peña C, Rodriguez de Lores Arnaiz G. Endogenous modulators of brain Na+,K(+)-ATPase at early postnatal stages of rat development. Int J Dev Neurosci 1998; 16:97-101. [PMID: 9762582 DOI: 10.1016/s0736-5748(98)00006-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The presence of endogenous modulators (peaks I and II) of synaptosomal Na+, K(+)-ATPase activity from adult rat cerebral cortex was previously suggested. In this study, the presence of such modulators at different postnatal stages of rat development was examined and their effect was tested on Na+, K(+)-ATPase activity. Synaptosomal membrane Na+, K(+)-ATPase activity was enhanced 20-30% by peak I and inhibited 70-75% by peak II obtained from 4-, 10-, 20- and 35-40-day-old rats. A fraction purified from peak II by anionic exchange HPLC (termed II-E) highly inhibits enzyme activity and behaves as a ouabain-like factor. Inhibitory activity of a 4-day-old II-E fraction proved higher than the corresponding fraction obtained from adult rats. Since expression of cerebral Na+, K(+)-ATPase has been shown to increase 10-fold during development whereas peak II concentration was observed to remain constant, and given the higher potency of purified neonatal II-E fraction, the effect of the latter may be greater at early postnatal stages of development than during adult life. It is suggested that the II-E fraction, which contains an ouabain-like factor, may play a role in neuronal development.
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Affiliation(s)
- M A Calviño
- Instituto de Biología Celular y Neurociencias Prof. E. De Robertis, Facultad de Medicina, Universidad de Buenos Aires, Argentina
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172
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Borok Z, Danto SI, Dimen LL, Zhang XL, Lubman RL. Na(+)-K(+)-ATPase expression in alveolar epithelial cells: upregulation of active ion transport by KGF. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:L149-58. [PMID: 9458813 DOI: 10.1152/ajplung.1998.274.1.l149] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We evaluated the effects of keratinocyte growth factor (KGF) on alveolar epithelial cell (AEC) active ion transport and on rat epithelial Na channel (rENaC) subunit and Na(+)-K(+)-adenosinetriphosphatase (ATPase) subunit isoform expression using monolayers of AEC grown in primary culture. Rat alveolar type II cells were plated on polycarbonate filters in serum-free medium, and KGF (10 ng/ml) was added to confluent AEC monolayers on day 4 in culture. Exposure of AEC monolayers to KGF on day 4 resulted in dose-dependent increases in short-circuit current (Isc) compared with controls by day 5, with further increases occurring through day 8. Relative Na(+)-K(+)-ATPase alpha 1-subunit mRNA abundance was increased by 41% on days 6 and 8 after exposure to KGF, whereas alpha 2-subunit mRNA remained only marginally detectable in both the absence and presence of KGF. Levels of mRNA for the beta 1-subunit of Na(+)-K(+)-ATPase did not increase, whereas cellular alpha 1- and beta 1-subunit protein increased 70 and 31%, respectively, on day 6. mRNA for alpha-, beta-, and gamma-rENaC all decreased in abundance after treatment with KGF. These results indicate that KGF upregulates active ion transport across AEC monolayers via a KGF-induced increase in Na pumps, primarily due to increased Na(+)-K(+)-ATPase alpha 1-subunit mRNA expression. We conclude that KGF may enhance alveolar fluid clearance after acute lung injury by upregulating Na pump expression and transepithelial Na transport across the alveolar epithelium.
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Affiliation(s)
- Z Borok
- Will Rogers Institute Pulmonary Research Center, Division of Pulmonary and Critical Care Medicine, University of Southern California, Los Angeles 90033, USA
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173
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Chauhan NB, Lee JM, Siegel GJ. Na,K-ATPase mRNA levels and plaque load in Alzheimer's disease. J Mol Neurosci 1997; 9:151-66. [PMID: 9481617 DOI: 10.1007/bf02800498] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
UNLABELLED The expression of Na,K-ATPase alpha 1- and alpha 3-mRNAs was analyzed by in situ hybridization in the superior frontal cortex and cerebellum of brains from five Alzheimer's disease (AD), five nondemented age-matched, and three young control subjects. Brains with well-preserved RNA, tested by Northern hybridization of immobilized RNA with [32P]-labeled human beta-actin riboprobe, were chosen for analysis. In situ hybridization was performed on formalin-fixed, 5 microns-thick Paraplast sections with [35S]-labeled riboprobes prepared by in vitro transcription of the respective linearized clones: a 537-bp EcoRI-PstI fragment of alpha 1-cDNA and a 342-bp PstI-EcoRI fragment of alpha 3-cDNA. In cortex, grains related to mRNA were measured by density per unit area in five cortical columns separated by 1.0-1.2 cm in each of two adjacent sections. Each cortical column of 180-micron width was divided into four depths orthogonal to the pial surface between the pia and the white matter. Amyloid plaques were counted in the same regions of adjacent sections. In addition, alpha 3-mRNA grain clusters over individual pyramidal neurons within depth 4 were analyzed. We found the following significant changes (p < 0.05): 1. Increases in total alpha 1-mRNA by 13-19% in AD compared to young and by 7-12% in AD compared to age-matched controls. 2. Decrease in total alpha 3-mRNA by 31-38% in AD compared to young and age-matched controls. 3. Decrease in alpha 3-mRNA content over individual pyramidal perikarya by 14% in normal aged brains without plaques compared to young controls, and by 44% in AD relative to young controls and by 35% compared to age-matched controls. No significant difference (p < 0.2) was found with respect to alpha 1- or alpha 3-mRNA in cerebellar cortex or individual Purkinje cells among any of the groups. In addition, there was a trend toward an inverse correlation between the levels of alpha 3-mRNA and of diffuse plaques, but not of neuritic plaques, in AD cases. IN CONCLUSION 1. The increases in alpha 1-mRNA in AD may be related to an increased reactive gliosis. 2. The declines in alpha 3-mRNA per individual neuron found in normal aging occur prior to the formation of diffuse plaques and are greatly accelerated in AD. 3. The declines in alpha 3-mRNA per neuron found in normal aging may predispose to or potentiate AD pathogenesis.
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Affiliation(s)
- N B Chauhan
- Molecular and Cellular Neuroscience Laboratory, Edward Hines Jr. Veterans Affairs Hospital, IL 60141, USA
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174
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Ridge K, Olivera W, Rutschman DH, Mercer RW, Uhal B, Horowitz S, Hughes F, Factor P, Barnard ML, Sznajder JI. Alpha-2 Na,K-ATPase contributes to lung liquid clearance. Ann N Y Acad Sci 1997; 834:651-2. [PMID: 9405882 DOI: 10.1111/j.1749-6632.1997.tb52340.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- K Ridge
- Pulmonary and Critical Care Medicine Division, Michael Reese Hospital, Chicago, Illinois 60616, USA
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175
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Vér A, Szántó I, Bányász T, Csermely P, Végh E, Somogyi J. Changes in the expression of Na+/K+-ATPase isoenzymes in the left ventricle of diabetic rat hearts: effect of insulin treatment. Diabetologia 1997; 40:1255-62. [PMID: 9389416 DOI: 10.1007/s001250050818] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Na+/K+-ATPase related strophanthidin sensitive 3-O-methylfluorescein-phosphatase activity, [3H]ouabain binding and expression of Na+/K+-ATPase subunit isoforms were measured in the left ventricle of the heart of normal and streptozotocin-diabetic rats with and without insulin treatment. Compared to control animals, the enzyme activity was 0.75 +/- 0.09 and 0.62 +/- 0.06 times lower in rats diabetic for 2 and for 4 weeks, respectively. This was associated with a proportional decrease of the [3H]ouabain binding sites. Immunoblots indicated a 0.76 +/- 0.08 and 0.61 +/- 0.08-fold decrease of alpha1, a 0.68 +/- 0.09 and 0.41 +/- 0.04-fold decrease of alpha2 subunit in 2- and 4-week diabetic rats, respectively relative to controls. Beta1 subunit decreased proportionally 0.71 +/- 0.07 and 0.38 +/- 0.06-fold, and beta2 decreased 0.75 +/- 0.08 and 0.31 +/- 0.06-fold, respectively. Northern blot analysis revealed a significant reduction in mRNA level of Na+/K+-ATPase subunit isoforms after 2 and 4 weeks of diabetes (for alpha1 66.2 +/- 8.2 and 55.9 +/- 7.8% of controls for alpha2 91.7 +/- 12.1 and 41.1 +/- 7.1% of controls and for beta subunit 93.4 +/- 11.1 and 49.8 +/- 6.8% of controls, respectively). Although, mRNA levels of isoform reverted to even higher levels than the control values after insulin treatment, insulin caused only a partial recovery of enzyme activity, [3H]ouabain binding capacity and protein expression. We have obtained evidence that in cardiac left ventricle there are more than one type of Na+/K+-ATPase alpha and beta subunit isoforms which are affected in diabetes and by insulin treatment. The time course of diabetes induced changes and the degree of involvement suggest that the Na+/K+-ATPase isoforms are altered individually.
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Affiliation(s)
- A Vér
- Semmelweis University of Medicine, Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Budapest, Hungary
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176
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Uochi T, Takahashi S, Ninomiya H, Fukui A, Asashima M. The Na+,K+-ATPase alpha subunit requires gastrulation in the Xenopus embryo. Dev Growth Differ 1997; 39:571-80. [PMID: 9338592 DOI: 10.1046/j.1440-169x.1997.t01-4-00004.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Na+,K+-ATPase participates in reabsorption of ions and water and produces an electrochemical gradient between the intra- and extracellular spaces across the cell membrane. It also plays an important role in many developmental phenomena such as a blastocoele formation and neural formation. To elucidate the expression pattern of Na+,K+-ATPase in the Xenopus embryo, the spatial expression patterns of the Na+,K+-ATPase alpha subunit were studied in a normal embryo by whole-mount in situ hybridization. These transcripts were localized around the dorsal blastopore at the gastrula stage, in the neural tube at the neurula stage, and then in the pronephros and cloaca at the tail-bud stage. To study the function of Na+,K+-ATPase in embryogenesis after mid-blastula transition, the expression of the Na+,K+-ATPase alpha subunit was inhibited by the injection of specific antisense RNA. Embryos injected with Na+,K+-ATPase antisense RNA showed inhibition of gastrulation. When antisense RNA was injected into the dorsal blastomeres, head differentiation was markedly inhibited. These results suggest that this transcript plays an important role during gastrulation and head differentiation.
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Affiliation(s)
- T Uochi
- Department of Life Science (Biology), The University of Tokyo, Japan
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177
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Barquin N, Ciccolella DE, Ridge KM, Sznajder JI. Dexamethasone upregulates the Na-K-ATPase in rat alveolar epithelial cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:L825-30. [PMID: 9357858 DOI: 10.1152/ajplung.1997.273.4.l825] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Previous studies in kidney, heart, and liver cells have demonstrated that dexamethasone regulates the expression of Na-K-ATPase. In the lungs, Na-K-ATPase has been reported in alveolar epithelial type II (ATII) cells and is thought to participate in active Na+ transport and lung edema clearance. The aim of this study was to determine whether Na-K-ATPase would be regulated by dexamethasone in cultured rat ATII cells. Regulation of the Na-K-ATPase by dexamethasone could lead to a greater understanding of its role in active Na+ transport and lung edema clearance. Rat ATII cells were isolated, plated for 24 h, and exposed to 10(-7) and 10(-8) M dexamethasone. These cells were harvested at 0, 3, 6, 12, and 24 h after dexamethasone exposure for determination of steady-state Na-K-ATPase mRNA transcript levels, protein expression, and function. The steady-state Na-K-ATPase beta1-mRNA transcript levels increased in ATII cells 6, 12, and 24 h after dexamethasone exposure (P < 0.05). However, the steady-state alpha1-mRNA transcript levels were unchanged. The protein expression for the alpha1- and beta1-subunits increased in ATII cells exposed to dexamethasone compared with controls in association with a temporal increase in Na-K-ATPase function after dexamethasone exposure. These results suggest that dexamethasone regulates Na-K-ATPase in ATII cells possibly by transcriptional, translational, and posttranslational mechanisms.
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Affiliation(s)
- N Barquin
- Pulmonary and Critical Care Medicine, Michael Reese Hospital and Medical Center, Chicago, Illinois 60616, USA
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178
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Book CB, Sun X, Ng YC. Developmental changes in regulation of the Na+, K(+)-ATPase alpha 3 isoform by thyroid hormone in ferret heart. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1358:172-80. [PMID: 9332453 DOI: 10.1016/s0167-4889(97)00067-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ferret heart expresses the alpha 1- as well as the alpha 3-isoform of the Na+, K(+)-ATPase. We have shown previously that the alpha 3 isoform is differentially upregulated during postnatal cardiac development and that in adult ferrets expression of alpha 3 is not responsive to regulation by thyroid hormone (TH). Since developmental-stage dependent effects of TH have been reported previously, the present study examined whether effects of TH on expression of the Na+, K(+)-ATPase isoforms in ferret heart is modulated during development and possible mechanisms were examined. Ferrets of different age groups were treated with TH and the relative abundance of Na+, K(+)-ATPase isoforms in ferret myocardium was determined by immunoblotting. Thyroid hormone (T3; 50 micrograms/100 g body weight on 3 alternating days, s.c.) increased protein levels of the alpha 3 isoform, but not that of alpha 1 or beta 1, in myocardium of 5-day-old and 3-week-old ferrets. By contrast, in myocardium of 6- and 8-week-old ferrets T3 failed to increase protein levels of alpha 1 and alpha 3. To determine whether elevated plasma levels of TH during development plays a role in the transition, mature ferrets were first made hypothyroid before TH treatment. In these hypothyroid ferrets expression of the alpha 3 isoform remained unresponsive to TH (T4, 0.5 mg/kg for 7 days, s.c.). The transition from TH-responsive to TH-unresponsive appears to be isoform-specific because in skeletal muscle of 8-week-old ferrets and in hypothyroid ferrets the alpha 2 isoform is upregulated by TH. Finally, there appears to be functional thyroid hormone receptors throughout development because in each age group TH effectively induced expression of alpha-MHC in the myocardium. In conclusion, these findings demonstrate that expression of alpha 3 isoform in the myocardium of newborn ferret is responsive to TH; however, the responsiveness terminates between 3- and 6-weeks of age. Neither elevated endogenous TH level nor a lack of functional thyroid hormone receptor appears to be responsible for the transition from TH-responsive to TH-unresponsive.
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Affiliation(s)
- C B Book
- Department of Pharmacology, College of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033, USA
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179
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Arystarkhova E, Sweadner KJ. Tissue-specific expression of the Na,K-ATPase beta3 subunit. The presence of beta3 in lung and liver addresses the problem of the missing subunit. J Biol Chem 1997; 272:22405-8. [PMID: 9278390 DOI: 10.1074/jbc.272.36.22405] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Na,K-ATPase belongs to a family of P-type ion-translocating ATPases sharing homologous catalytic subunits (alpha) that traverse the membrane several times and contain the binding sites for ATP and cations. In this family, only Na,K- and H,K-ATPases have been shown to have a second subunit, a single-span glycoprotein called beta. Recently a new isoform (beta3) has been identified in mammals. Here we describe structural features and tissue distribution of the beta3 protein, utilizing an antiserum specific for its N terminus. beta3 was the only beta detected in Na,K-ATPase purified from C6 glioma. Treatment with N-glycosidase F confirmed that beta3 is a glycoprotein containing N-linked carbohydrate chains. Molecular masses of the glycosylated protein and core protein were estimated to be 42 and 35 kDa, respectively, which are different from those of the beta1 and beta2 subunits. Detection of beta subunits has historically been difficult in certain tissues. Sensitivity was improved by deglycosylating, and expression was evaluated by obtaining estimates of beta3/alpha ratio. The proportion of beta3 protein in the rat was highest in lung and testis. It was also present in liver and skeletal muscle, whereas kidney, heart, and brain contained it only as a minor component of the Na,K-ATPase. In P7 rat, we found skeletal muscle and lung Na,K-ATPase to be the most enriched in beta3 subunit, whereas expression in liver was very low, illustrating developmentally regulated changes in expression. The substantial expression in lung and adult liver very likely explains long-standing puzzles about an apparent paucity of beta subunit in membranes or in discrete cellular or subcellular structures.
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Affiliation(s)
- E Arystarkhova
- Laboratory of Membrane Biology, Neuroscience Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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180
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Dagenais A, Kothary R, Berthiaume Y. The alpha subunit of the epithelial sodium channel in the mouse: developmental regulation of its expression. Pediatr Res 1997; 42:327-34. [PMID: 9284273 DOI: 10.1203/00006450-199709000-00013] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Sodium reabsorption by the amiloride-sensitive sodium channel of epithelial cells plays a crucial role in the management of ionic composition and fluid volume in the body. In the respiratory system, sodium transport is involved in the clearance of pulmonary edema and of liquid secreted during fetal life at birth. We have cloned a partial cDNA of the alpha subunit of the mouse amiloride-sensitive sodium channel (alpha mENaC). In the region of comparison, the mouse alpha subunit shows 92% identity at the DNA level and 95% identity at the amino acid level with the rat sequence. The kidneys, lungs, and distal colon are major sites of expression of a 3.5-kb alpha mENaC mRNA. During mouse development, alpha mENaC transcripts appear late during gestation (d 17.5) and are expressed continuously thereafter. In the distal colon, a short 1.2-kb mRNA deleted of the 5' part of the transcript is detected during gestation and is replaced gradually by the mature 3.5-kb transcript after birth. Alpha mENaC and alpha1 Na+-K+-ATPase mRNAs have an expression profile that is modulated similarly during development for a given tissue. The expression of alpha mENaC transcripts increases transiently in the lungs at birth (2.5-fold), as for alpha1 Na+-K+-ATPase mRNAs (1.5-fold), suggesting that the expression of several components of the sodium transport system is modulated in the lungs at that time. In the kidney, there is no significant increase of alpha mENaC and alpha1 Na+-K+-ATPase mRNAs in newborns.
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MESH Headings
- Amino Acid Sequence
- Animals
- Animals, Newborn/genetics
- Base Sequence
- Cloning, Molecular
- Colon/chemistry
- Colon/physiology
- DNA Probes/genetics
- Epithelial Sodium Channels
- Female
- Fetus/chemistry
- Gene Expression Regulation, Developmental/genetics
- Gene Expression Regulation, Developmental/physiology
- Gestational Age
- Kidney/chemistry
- Kidney/physiology
- Lung/chemistry
- Lung/physiology
- Mice
- Mice, Inbred Strains
- Molecular Sequence Data
- Polymerase Chain Reaction/methods
- Pregnancy
- RNA, Messenger/analysis
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Sodium Channels/chemistry
- Sodium Channels/genetics
- Sodium Channels/physiology
- Sodium-Potassium-Exchanging ATPase/genetics
- Sodium-Potassium-Exchanging ATPase/physiology
- Transcription, Genetic/genetics
- Transcription, Genetic/physiology
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Affiliation(s)
- A Dagenais
- Centre de Recherche Hôtel-Dieu de Montréal, Département de Médecine, Université de Montréal, Quebec, Canada
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181
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Nemoto J, Muto S, Ohtaka A, Kawakami K, Asano Y. Serum transcriptionally regulates Na(+)-K(+)-ATPase gene expression in vascular smooth muscle cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:C1088-99. [PMID: 9316431 DOI: 10.1152/ajpcell.1997.273.3.c1088] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The present study was designed to examine the effects of serum on Na(+)-K(+)-ATPase alpha 1- and beta 1-subunit gene expression in cultured vascular smooth muscle cells (VSMC) from rat thoracic aortas. Addition of 10% serum to VSMC for 24 h increased Na(+)-K(+)-ATPase activity 1.5-fold and alpha 1- and beta 1-subunit protein levels 1.9-fold. Serum (10%) caused a 3.5-fold increase in alpha 1-mRNA levels and a 6.7-fold increase in beta 1-mRNA levels, with peak elevations at 12 h. The protein synthesis inhibitor cycloheximide abolished serum-mediated beta 1-mRNA induction but did not affect serum-mediated alpha 1-mRNA induction. Protein kinase C (PKC) inhibitors (staurosporine A or calphostin C) or tyrosine kinase (TK) inhibitors (genistein or herbimycin A) significantly reduced serum-mediated beta 1-mRNA induction but had no effect on serum-mediated alpha 1-mRNA induction. Transfection experiments with the 5'-flanking sequences of the alpha 1- or beta 1-subunit genes linked to the luciferase reporter gene revealed that 10% serum caused 2.8- and 6.5-fold increases in luciferase activity, respectively. Among growth factors, only basic fibroblast growth factor (FGF) enhanced luciferase activities for the alpha 1- and beta 1-subunit genes. We conclude that 1) serum stimulates alpha 1- and beta 1-mRNA expression, alpha 1- and beta 1-subunit protein accumulation, and Na(+)-K(+)-ATPase activity; 2) serum-mediated beta 1-mRNA induction partly requires de novo synthesis of intermediate regulatory proteins and activation of PKC and TK, whereas serum-mediated alpha 1-mRNA induction occurs through PKC- and TK-independent mechanisms; 3) the 5'-flanking regions of the alpha 1- and beta 1-subunit genes are serum responsive; and 4) FGF mimics stimulatory effects of serum on promoter activities for the alpha 1- and beta 1-subunit genes.
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MESH Headings
- Animals
- Aorta, Thoracic/cytology
- Aorta, Thoracic/enzymology
- Blood
- Cattle
- Cell Division
- Cells, Cultured
- Culture Media
- Cycloheximide/pharmacology
- DNA/biosynthesis
- Enzyme Induction
- Fibroblast Growth Factors/pharmacology
- Gene Expression Regulation, Enzymologic
- Growth Substances/pharmacology
- Insulin/pharmacology
- Kinetics
- Male
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/enzymology
- Platelet-Derived Growth Factor/pharmacology
- Polymerase Chain Reaction
- RNA, Messenger/biosynthesis
- Rats
- Rats, Sprague-Dawley
- Sodium-Potassium-Exchanging ATPase/biosynthesis
- Thymidine/metabolism
- Transcription, Genetic/drug effects
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Affiliation(s)
- J Nemoto
- Department of Nephrology, Jichi Medical School, Tochigi, Japan
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182
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Kanoh N. Cytochemical localization of ouabain-sensitive, K(+)-dependent p-nitrophenylphosphatase activity in the facial nerve of reserpinized guinea pigs. J Histochem Cytochem 1997; 45:1129-35. [PMID: 9267473 DOI: 10.1177/002215549704500810] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Ion-transporting Na,K-ATPase plays an essential role in nerve conduction. To clarify the cytochemical effects of reserpine on transport Na,K-ATPase activity, the localization of ouabain-sensitive, K(+)-dependent p-nitrophenylphosphatase (K-NPPase) activity was investigated in the facial nerves of normal and reserpinized guinea pigs using a cerium-based method. In the normal facial nerve, the reaction product of K-NPPase activity was observed on the internodal axolemma and Schmidt-Lanterman incisures. In the Ranvier nodes, enzyme activity was localized to the paranodal and nodal axolemma. In the reserpinized nerves, reaction product was detectable on the nodal axolemma but was undetectable on the other parts of the axolemma. Nodal K-NPPase was not affected by reserpine treatment. Therefore, the transport Na,K-ATPase on the nodal axolemma might differ from that on the other parts of the axolemma. Allowing reserpinized animals to survive. Two different ouabain-sensitive K-NPPase reactivities, "reserpine-sensitive" and "reserpine-resistant," might be present in the facial nerve of guinea pigs.
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Affiliation(s)
- N Kanoh
- Department of Otolaryngology, Hyogo College of Medicine, Japan
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183
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Billecocq A, Horne WC, Chakraborty M, Takeyasu K, Levenson R, Baron R. 1,25-Dihydroxyvitamin D3 selectively induces increased expression of the Na,K-ATPase beta 1 subunit in avian myelomonocytic cells without a concomitant change in Na,K-ATPase activity. J Cell Physiol 1997; 172:221-9. [PMID: 9258343 DOI: 10.1002/(sici)1097-4652(199708)172:2<221::aid-jcp9>3.0.co;2-q] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Treatment of avian myelomonocytic cells with 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) results in an approximately two fold increase in levels of Na,K-ATPase beta 1 subunit mRNA and protein (both total and plasma membrane-associated). The changes in beta 1 subunit expression occur in the absence of a detectable increase in expression of any of the three alpha subunit isoforms or in Na,K-ATPase activity. The selective induction of the expression of the beta subunit in avian myelomonocytic cells by 1,25(OH)2D3 reveals a previously unobserved feature of the regulation of Na,K-ATPase expression, while the targeting of beta subunit polypeptides to the plasma membrane in the absence of a corresponding increase in active Na,K-ATPase suggests that, in these cells, transport of the beta subunit to the plasma membrane may be independent of its binding to the alpha subunit.
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Affiliation(s)
- A Billecocq
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8044, USA
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184
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Choi Y, Dubel SJ, Pacioaiou ML, Omori A, Ito T, Copeland TD, Takahashi M, McEnery MW. Parallel detection of Na,K-ATPase alpha subunit isoforms by pan-specific monoclonal mAb 9A7. Arch Biochem Biophys 1997; 344:165-75. [PMID: 9244394 DOI: 10.1006/abbi.1997.0183] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
While emphasis has been placed upon those proteins which either mediate or respond to the rapid influx of calcium following depolarization, there has been little emphasis upon those proteins which aid in the reequilibration of the membrane potential. In an effort to identify presynaptic membrane proteins implicated in neurosecretion, monoclonal antibodies were screened against proteins which cosegregated with neuronal voltage-dependent calcium channels (VDCC) following immunoprecipitation. One monoclonal antibody (mAb 9A7) identified a 110-kDa protein. Micropeptide sequencing of (i) the mAb 9A7 immunoaffinity purified antigen and (ii) the 110-kDa protein present in the neuronal (N-type) VDCC preparation (McEnery et al., 1991, Proc. Natl. Acad. Sci. 88, 11095-11099) indicated identity with the alpha subunit(s) of the Na,K-ATPase. Further characterization by Western blotting, immunochemical localization, and immunoaffinity purification indicated that mAb 9A7 not only recognized the alpha3 isoform which is predominant in neuronal tissues but also identified the alpha1 and alpha2 isoforms. mAb 9A7 exhibited a wide cross-species reactivity and recognized human, rat, and mouse alpha subunit isoforms at an internal epitope. The pan-specificity of mAb 9A7 and the differential mobility of the alpha1 isoform relative to the alpha2 and alpha3 permitted parallel detection of multiple alpha isoforms. Western blot analysis of undifferentiated rat pheochromocytoma cell line (PC12) and human neuroblastoma (IMR32) cells indicated coexpression of the alpha1 and alpha3 isozymes. Upon differentiation of IMR32 cells by dibutrylyl-cAMP, a substantial increase in the alpha3 relative to the alpha1 isoform was observed. While the enrichment of total Na,K-ATPase may reflect the increased demand for ATP-dependent ion transport as IMR32 cells become more excitable, the specific increase in the alpha3 isoform suggests a unique role of this isoform during IMR32 cell differentiation.
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Affiliation(s)
- Y Choi
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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185
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Gloor SM. Relevance of Na,K-ATPase to local extracellular potassium homeostasis and modulation of synaptic transmission. FEBS Lett 1997; 412:1-4. [PMID: 9257678 DOI: 10.1016/s0014-5793(97)00774-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The ion gradients generated by the Na,K-ATPase are essential for Na+-coupled transport systems, osmoregulation and restoration of ion concentrations in excitable tissues. Indirectly, the sodium pump controls intracellular Ca2+ concentration through the Na/Ca exchanger. In the nervous system various neurotransmitters can modulate Na,K-ATPase activity. The great diversity of Na,K-ATPase subunit isoforms, their complex spatial and temporal regulation of expression and their cellular localisation imply a functional role of the sodium pump in different regulatory pathways. Among these, potassium homeostasis and modulation of synaptic transmission are discussed here.
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Affiliation(s)
- S M Gloor
- Biochemistry II, Swiss Federal Institute of Technology, ETH Center, Zurich.
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186
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Murakami Y, Ikeda U, Shimada K, Kawakami K. Promoter of the Na,K-ATPase alpha3 subunit gene is composed of cis elements to which NF-Y and Sp1/Sp3 bind in rat cardiocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1352:311-24. [PMID: 9224955 DOI: 10.1016/s0167-4781(97)00032-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Na,K-ATPase alpha subunit has three isoforms whose expression is regulated developmentally and hormonally. Na,K-ATPase alpha3 subunit gene (Atpla3) is expressed only in brain and neonatal heart in a rat. The purpose of this study is to analyze cis-acting elements and trans-acting factors regulating the transcription of Atpla3 in cultured neonatal rat cardiocytes. Transient transfection assays with Atpla3-luciferase chimeric construct and a series of 5' sequential deletion mutations revealed the existence of positive regulatory elements from -74 to -59 and from -59 to -39. A factor was identified to bind across -59 by gel retardation assay. Methylation interference and DNase I footprinting analyses revealed the binding region from -74 to -53 (positive regulatory element (PRE) 1). The binding factor was identified to be NF-Y by gel retardation assay using specific antibody. Gel retardation and methylation interference analyses revealed that factors bind to two other elements from -54 to -43 (PRE2) and from -25 to -13 (PRE3). The binding factors were identified to be Sp1/Sp3 using specific antibodies. The functions of above-mentioned three elements were examined by transient transfection assay with various combinations of mutations. They all regulated the transcription positively and a synergistic enhancement of it was observed. Roles of NF-Y in the transcriptional activation and synergy are discussed.
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Affiliation(s)
- Y Murakami
- Department of Biology, Jichi Medical School, Kawachi, Tochigi, Japan
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187
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Liu X, Songu-Mize E. Alterations in alpha subunit expression of cardiac Na+,K+-ATPase in spontaneously hypertensive rats: effect of antihypertensive therapy. Eur J Pharmacol 1997; 327:151-6. [PMID: 9200553 DOI: 10.1016/s0014-2999(97)89654-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The alpha-2 subunit abundance of Na+,K(+)-ATPase in the rat heart has been reported to be reduced in several induced hypertensive models. To determine whether this reduction also occurs in a genetic model of hypertension, we studied expression of the alpha subunits in left ventricles of spontaneously hypertensive rats (SHR), and normotensive Wistar-Kyoto (WKY) and Sprague-Dawley rats using Western blotting and quantitative dot-blotting analysis with monoclonal antibodies. While the alpha-1 subunit was not affected in any of the strains, a significant reduction of the alpha-2 subunit expression was noted in 19-week-old SHRs, but not in age-matched WKY and Sprague-Dawley rats, supporting the hypothesis that elevated arterial pressure may differentially downregulate the alpha-2 subunit in the rat heart. To further test this hypothesis we designed experiments in which hypertensive rats were treated with the antihypertensive agents hydralazine and nifedipine. Both agents effectively normalized the blood pressure in the SHRs with no significant effect on the blood pressure in the WKY and Sprague-Dawley rats. The alpha-2 subunit in SHRs treated with hydralazine and nifedipine showed a 63.3% (n = 6, P < 0.05, analysis of variance and Fischer's test) and a 27.4% increase, respectively, over the hypertensive SHR controls, although the reversal effect of nifedipine did not quite reach significance. The alpha-1 subunit expression was not affected by any of the drug treatments. No effect of either of the drugs on the alpha-1 or alpha-2 subunit was observed in the WKY or Sprague-Dawley rat groups. These data support our hypothesis that the alpha-2 subunit may be a pressure-sensitive isoform of the cardiac Na+,K(+)-ATPase and that high blood pressure is, directly or indirectly, responsible for the reduction of the alpha-2 subunit protein expression.
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Affiliation(s)
- X Liu
- Department of Pharmacology and Experimental Therapeutics, Louisiana State University Medical Center, New Orleans 70112, USA
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188
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Overdier DG, Ye H, Peterson RS, Clevidence DE, Costa RH. The winged helix transcriptional activator HFH-3 is expressed in the distal tubules of embryonic and adult mouse kidney. J Biol Chem 1997; 272:13725-30. [PMID: 9153225 DOI: 10.1074/jbc.272.21.13725] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The hepatocyte nuclear factor-3 (HNF-3)/fork head homolog (HFH) proteins are an extensive family of transcription factors, which share homology in the winged helix DNA binding domain. Members of the HFH/winged helix family have been implicated in cell fate determination during pattern formation, in organogenesis, and in cell-type-specific gene expression. In this study we isolated a full-length HFH-3 cDNA clone from a human kidney library which encoded a 351-amino acid protein containing a centrally located winged helix DNA binding domain. We demonstrate that HFH-3 is a potent transcriptional activator requiring 138 C-terminal residues for activity. We used in situ hybridization to demonstrate that HFH-3 expression is restricted to the epithelium of the renal distal convoluted tubules. We determined the HFH-3 DNA binding consensus sequence by in vitro DNA binding site selection using recombinant HFH-3 protein and used this consensus sequence to identify putative HFH-3 target genes expressed there. These putative HFH-3 target genes include the Na/K-ATPase, Na/H and anion exchangers, E-cadherin, and mineralocorticoid receptor genes as well as genes for the transcription factors HNF-1, vHNF-1, and HNF-4.
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Affiliation(s)
- D G Overdier
- Department of Biochemistry, University of Illinois, Chicago, Illinois 60612-7334, USA
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189
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Vassallo DV, Songu-Mize E, Rossoni LV, Amaral SM. Effects of ouabain on vascular reactivity. Braz J Med Biol Res 1997; 30:545-52. [PMID: 9251776 DOI: 10.1590/s0100-879x1997000400016] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Ouabain is an endogenous substance occurring in the plasma in the nanomolar range, that has been proposed to increase vascular resistance and induce hypertension. This substance acts on the alpha-subunit of Na+,K(+)-ATPase inhibiting the Na(+)-pump activity. In the vascular smooth muscle this effect leads to intracellular Na+ accumulation that reduces the activity of the Na+/Ca2+ exchanger and to an increased vascular tone. It was also suggested that circulating ouabain, even in the nanomolar range, sensitizes the vascular smooth muscle to vasopressor substances. We tested the latter hypothesis by studying the effects of ouabain in the micromolar and nanomolar range on phenylephrine (PE)-evoked pressor responses. The experiments were performed in normotensive and hypertensive rats in vivo, under anesthesia, and in perfused rat tail vascular beds. The results showed that ouabain pretreatment increased the vasopressor responses to PE in vitro and in vivo. This sensitization after ouabain treatment was also observed in hypertensive animals which presented an enhanced vasopressor response to PE in comparison to normotensive animals. It is suggested that ouabain at nanomolar concentrations can sensitize vascular smooth muscle to vasopressor stimuli possibly contributing to increased tone in hypertension.
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Affiliation(s)
- D V Vassallo
- Departamento de Ciências Fisiológicas, Universidade Federal do Espírito Santo, Vitória, Brasil
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190
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Filippatos GS, Hughes WF, Qiao R, Sznajder JI, Uhal BD. Mechanisms of liquid flux across pulmonary alveolar epithelial cell monolayers. In Vitro Cell Dev Biol Anim 1997; 33:195-200. [PMID: 9112128 DOI: 10.1007/s11626-997-0141-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Active transport of sodium by pulmonary alveolar epithelial cells (AEC) is believed to be an important component of edema clearance in the normal and injured lung. Data supporting this premise have come from measurements of sodium movement across AEC monolayers or from perfused lung model systems. However, direct measurement of fluid flux across AEC monolayers has not been reported. In the present work, AEC were studied with an experimental system for the measurement of fluid flux (Jv) across functionally intact cell monolayers. Primary adult rat type II alveolar epithelial cells were cultured on 0.8 micron nuleopore filters previously coated with gelatin and fibronectin. Intact monolayers were verified by high electrical resistance (> 1000 omega) at 4-5 d of primary culture. At the same time interval, transmission electron microscopy revealed cells with type I cell-like morphology throughout the monolayer. These were characterized by both adherens and tight junctional attachments. Fluid flux across the monolayers was measured volumetrically over a period of 2 h in the presence of HEPES-buffered DMEM containing 3% fatty acid-free bovine serum albumin. Flux (Jv) was inhibited 39% by 1 X 10(-4) M ouabain (P < 0.01) and 27% by 5 X 10(-4) M amiloride (P < 0.05). These data support the concept that AEC Na+/K(+)-ATPase and Na+ transport systems are important determinants of AEC transepithelial fluid movement in vitro.
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Affiliation(s)
- G S Filippatos
- Department of Pharmacology and Anatomy, Rush Presbyterian-St. Luke's Medical Center, Rush Medical College, Chicago, Illinois 60612, USA
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191
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Pontiggia L, Gloor SM. The extracellular domain of the sodium pump beta isoforms determines complex stability with alpha 1. Biochem Biophys Res Commun 1997; 231:755-9. [PMID: 9070887 DOI: 10.1006/bbrc.1997.6188] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Both subunits of the Na,K-ATPase are encoded by several genes giving rise to at least six isozymes. To examine whether beta isoforms assemble with alpha 1 in a selective manner, we have overexpressed wild-type and chimeric beta subunits in L929 cells and examined assembly as a function of resistance towards detergent-mediated dissociation. In the presence of digitonin all beta chimeras coimmunoprecipitate the endogenous alpha 1 subunit. Only beta proteins with the ectodomain of beta 1 coimmunoprecipitate alpha 1 in the presence of Triton X-100. All beta chimeras stimulate Na,K-ATPase activity in L929 cells. These data indicate that the beta subunit ectodomains mediate interactions with alpha 1 and influence the stability of this complex.
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Affiliation(s)
- L Pontiggia
- Swiss Federal Institute of Technology, ETH Center, Zurich, Switzerland
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192
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Schmalzing G, Ruhl K, Gloor SM. Isoform-specific interactions of Na,K-ATPase subunits are mediated via extracellular domains and carbohydrates. Proc Natl Acad Sci U S A 1997; 94:1136-41. [PMID: 9037019 PMCID: PMC19757 DOI: 10.1073/pnas.94.4.1136] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The functional unit of the Na,K-ATPase consists of a catalytic alpha subunit noncovalently linked with a glycoprotein subunit, beta. Using ouabain binding assays and immunoprecipitation of rodent alpha/beta complexes, we show here that all six possible isozymes between three alpha and two beta isoforms can be formed in Xenopus oocytes. Two isoform-specific differences in alpha/beta interactions are observed: (i) alpha1/beta1 and alpha2/beta2 complexes, in contrast to alpha1/beta2 complexes, are stable against Triton X-100-mediated dissociation, and (ii) beta2 subunits must carry N-glycans to combine with alpha1 but not with alpha2. The interacting surfaces are mainly exposed to the extracellular side because coexpression of a truncated beta1 subunit comprising the ectodomain results in assembly with alpha1 and alpha2, but not with alpha3; the beta2 ectodomain combines with alpha2 only. A chimera consisting of 81% and 19% of the alpha1 N terminus and alpha2 C terminus, respectively, behaves like alpha2 and coprecipitates with the beta2 ectodomain. In contrast, the reciprocal chimera does not coprecipitate with the beta2 ectodomain. These results provide evidence for a selective interaction of Na,K-ATPase alpha and beta subunits.
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Affiliation(s)
- G Schmalzing
- Pharmakologisches Institut für Naturwissenschaftler, J. W. Goethe-Universität, Biozentrum N 260, Frankfurt, Germany
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193
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Thompson CB, McDonough AA. Skeletal muscle Na,K-ATPase alpha and beta subunit protein levels respond to hypokalemic challenge with isoform and muscle type specificity. J Biol Chem 1996; 271:32653-8. [PMID: 8955095 DOI: 10.1074/jbc.271.51.32653] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
During potassium deprivation, skeletal muscle loses K+ to buffer the fall in extracellular K+. Decreased active K+ uptake via the sodium pump, Na,K-ATPase, contributes to the adjustment. Skeletal muscle expresses alpha1, alpha2, beta1, and beta2 isoforms of the Na, K-ATPase alphabeta heterodimer. This study was directed at testing the hypothesis that K+ loss from muscle during K+ deprivation is a function of decreased expression of specific isoforms expressed in a muscle type-specific pattern. Isoform abundance was measured in soleus, red and white gastrocnemius, extensor digitorum longus, and diaphragm by immunoblot. alpha2 expression was uniform across control muscles, whereas alpha1 and beta1 were twice as high in oxidative (soleus and diaphragm) as in fast glycolytic (white gastrocnemius) muscles, and beta2 expression was reciprocal: highest in white gastrocnemius and barely detectable in soleus and diaphragm. Following 10 days of potassium deprivation plasma K+ fell from 4.0 to 2.3 mM, and there were distinct responses in glycolytic versus oxidative muscles. In glycolytic white gastrocnemius alpha2 and beta2 fell 94 and 70%, respectively; in mixed red gastrocnemius and extensor digitorum longus both fell 60%, and beta1 fell 25%. In oxidative soleus and diaphragm alpha2 fell 55 and 30%, respectively, with only minor changes in beta1. Although decreases in alpha2 and beta2 expression are much greater in glycolytic than oxidative muscles during K+ deprivation, both types of muscle lose tissue K+ to the same extent, a 20% decrease, suggesting that multiple mechanisms are in place to regulate the release of skeletal muscle cell K+.
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Affiliation(s)
- C B Thompson
- Department of Physiology and Biophysics, University of Southern California School of Medicine, Los Angeles, California 90033, USA
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194
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Yu HY, Nettikadan S, Fambrough DM, Takeyasu K. Negative transcriptional regulation of the chicken Na+/K(+)-ATPase alpha 1-subunit gene. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1309:239-52. [PMID: 8982261 DOI: 10.1016/s0167-4781(96)00130-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Although the Na+/K(+)-ATPase alpha 1-subunit gene is ubiquitously expressed in vertebrates, its level of expression varies among tissue and cell types. In spite of similar mRNA distribution in tissues of mammals and birds, the 5'-flanking regions of alpha 1-subunit genes exhibit remarkable diversity; i.e., the core promoter activity of the TATA-less chicken alpha 1 gene strongly depends upon multiple Sp1-based regulation (six Sp1 sites), whereas the promoter activity of the TATA-like rat alpha 1-subunit gene relies on the two Sp1 and additional positive regulatory factors. Further analysis of the regulatory regions of the Na+/K(+)-ATPase alpha 1-subunit genes revealed that the vertebrate alpha 1-subunit genes may share common inhibitory mechanisms for subtle transcriptional regulation; the core promoter activities can be either enhanced or repressed depending on the availability of inhibitory factors. Two potential candidates for such inhibitory elements in both avian and mammalian Na+/K(+)-ATPase alpha 1-subunit genes are (1) a newly identified element, GCCCTC, and (2) a GCF-binding sequence, NN[G/c]CG[G/c][G/c][G/c]CN, or its reverse complement. Gel retardation assays using the inhibitory region of the chicken gene and crude nuclear extracts from tissue-cultured chicken and mouse cells showed the existence of a set of proteins that bind to this region. The amounts of individual regulatory proteins in different cell types seem to vary, resulting in differential formation of DNA/protein complexes in different cell types. Thus, the regulation of Na+/K(+)-ATPase alpha 1-subunit gene expression under different cellular environment as well as in different cell types can be achieved by a shared mechanism; modulation of the ratio of the abundance of individual inhibitory factors.
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Affiliation(s)
- H Y Yu
- Department of Medical Biochemistry, Ohio State University, Columbus 43210, USA
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195
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Mitsunaga-Nakatsubo K, Yamazaki K, Hatoh-Okazaki M, Kawashita H, Okamura C, Akasaka K, Shimada H, Yasumasu I. cDNA cloning of Na+, K(+)-ATPase alpha-subunit from embryos of the sea urchin, Hemicentrotus pulcherrimus. Zoolog Sci 1996; 13:833-41. [PMID: 9107140 DOI: 10.2108/zsj.13.833] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Na+, K(+)-ATPase alpha-subunit cDNA of the sea urchin, Hemicentrotus pulcherrimus, was obtained by twice screening prism and gastrula lambda gt10 cDNA libraries using an oligonucleotide probe derived from a mostly conserved region, FSBA (5'-p-(fluorosulfonyl)-benzoyladenosine) binding site of cation transport ATPases. The 5'-end of the non-coding region was determined by primer extension and the region was amplified by 5'-RACE method. The sea urchin alpha-subunit cDNA consists of 4401 nucleotides and encodes 1038 amino acid residues (MW, 114 kDa). The predicted primary structure, except N-terminal region, has similar degree of high homology to various metazoan Na+, K(+)-ATPase alpha-subunits. Alignment of amino acid sequence and a hydropathy profile also predicts eight putative transmembrane segments at least. The phylogenetic tree suspected from alignment of amino acid sequences of 21 species suggests that sea urchin and vertebrate Na+, K(+)-ATPase alpha-subunits seem to have evolved from a common origin, before vertebrate alpha-subunit divided into three isoforms.
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196
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Schramm CM, Grunstein MM. Corticosteroid modulation of Na(+)-K+ pump-mediated relaxation in maturing airway smooth muscle. Br J Pharmacol 1996; 119:807-12. [PMID: 8922725 PMCID: PMC1915935 DOI: 10.1111/j.1476-5381.1996.tb15744.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
1. The ontogeny of the relaxant influence of the airway electrogenic Na(+)-K+ pump and its potential modulation by corticosteroids were examined in airway smooth muscle (ASM) segments isolated from newborn and adult rabbits. 2. Control and methylprednisolone-treated (MP) ASM segments were half-maximally contracted with methacholine in K(+)-free buffer and the ASM relaxant responses to Na(+)-K+ pump activation were subsequently evaluated. Relative to adult ASM, control newborn ASM showed significantly enhanced maximal relaxation (Rmax) to KCl (62.5 +/- 5.2% vs. 47.8 +/- 5.2%), but no difference in sensitivity (pC2 = -log concentration producing 50% Rmax: 2.18 +/- 0.12 vs. 2.29 +/- 0.09-log M). 3. Exposure of ASM segments to 500 microM methylprednisolone for 1 h potentiated the airway Na(+)-K+ pump activity. A more pronounced effect was obtained in newborn ASM, where both the Rmax and pC2 values were significantly enhanced. In mature ASM, only the Rmax response to KCl was increased in the presence of MP. 4. Collectively, these data demonstrate that: (i) the functional activity of the airway electrogenic Na(+)-K+ pump decreases with post-natal maturation in the rabbit: (ii) corticosteroid treatment potentiates Na(+)-K+ pump activity in rabbit ASM; and (iii) the latter effect of corticosteroids is enhanced in immature airways. 5. The above findings provide new evidence that the airway relaxant response to activation of the electrogenic Na(+)-K+ pump varies ontogenetically and that corticosteroids potentiate the Na(+)-K+ pump activity in an age-dependent manner.
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Affiliation(s)
- C M Schramm
- Pediatric Pulmonary Division, University of Connecticut School of medicine, Farmington 06030, USA
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197
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Michaut P, Planes C, Escoubet B, Clement A, Amiel C, Clerici C. Rat lung alveolar type II cell line maintains sodium transport characteristics of primary culture. J Cell Physiol 1996; 169:78-86. [PMID: 8841424 DOI: 10.1002/(sici)1097-4652(199610)169:1<78::aid-jcp8>3.0.co;2-b] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Culture of primary alveolar type II cells has been widely used to investigate the Na+ transport characteristics of alveolar epithelium. However, this model was restricted by early morphological and physiological dedifferentiation in culture. Recently, a cell line has been obtained by transfection of neonatal type II cells with the simian virus SV40 large T antigen gene (SV40-T2). SV40-T2 cells have retained proliferative characteristics of the primary type II cells (Clement et al., 1991, Exp. Cell Res., 196:198-205.) In the present study, we have characterized Na+ transport pathways in SV40-T2 cells. SV40-T2 cells retained most cardinal properties of the original alveolar epithelial cells. Na+ entry occurred, as in primary cultures, through both Na(+)-cotransporters and amiloride-sensitive Na+ channels. SV40-T2 cells expressed Na(+)-phosphate. Na(+)-amino acid and Na(+)-K(+)-Cl cotransports which are quantitatively similar to that of primary cultures. The existence of amiloride-sensitive Na+ channels was supported by molecular and functional data. SV40-T2 expressed the cloned alpha- and gamma-mRNAs for the rat epithelial Na+ channel (rENaC), whereas beta subunit was not detected, and 22Na+ influx was significantly inhibited by 10 microM amiloride. Na+, which enters SV40-T2 cells, is extruded through a Na+, K(+)-ATPase: mRNA for alpha 1 and beta 1 isoforms of Na+, K(+)-ATPase were present and Na+, K(+)-ATPase activity was evidenced either on intact cells by the presence of a ouabain-sensitive component of 86Rb+ influx or on cell homogenates by the measurement of ouabain-inhibitable ATP hydrolysis. These results indicate that SV40-T2 cell line displays most of the Na+ transport characteristics of well-differentiated primary cells in the first days of culture. We conclude that the SV40-T2 cell line provides a model of differentiated alveolar type II cells and may be a powerful tool to study, in vitro, the modulation of Na+ transport in pathophysiological conditions.
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Affiliation(s)
- P Michaut
- Department of Physiology, Faculté de Médecine Xavier Bichat, Université Denis Diderot, Paris, France
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198
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Slezak J, Schulze W, Stefankova Z, Okruhlicova L, Danihel L, Wallukat G. Localization of alpha 1,2,3-subunit isoforms of Na,K-ATPase in cultured neonatal and adult rat myocardium: the immunofluorescence and immunocytochemical study. Mol Cell Biochem 1996; 163-164:39-45. [PMID: 8974038 DOI: 10.1007/bf00408639] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
By indirect immunofluorescence and preembedding peroxidase-diaminobenzidine technique the localization of polyclonal and monoclonal antibodies against alpha 1, alpha 2 and alpha 3 isoforms of the Na,K-ATPase were studied in rat myocardium. The alpha 1-subunit was identified predominantly on sarcolemma of cultured myocytes, neonatal, as well as adult cardiocytes. The alpha 2 signal was localized around nuclei of cultured cardiocytes, very weak signals were seen in neonatal and more intense signal, were dispersed throughout the adult myocytes. The alpha 3-subunit immunoreactivity was weak and localized in cell processes connecting individual cultured cells, on sarcolemma and intercalated discs of neonatal cells and very weak in adult working myocytes. Cytochemically demonstrated ouabain resistant Na,K-ATPase localized in junctional sarcoplasmic reticulum may represent alpha 1 isoenzyme which is directly involved in modulation of action potential fluxes.
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Affiliation(s)
- J Slezak
- Institute for Heart Research, Slovak Academy of Sciences, Bratislava, Slovak Republic
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199
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Lee JS, Lee SW, Wallick ET. Different distribution of the α2 Na+, K+-ATPase isoform between rat atria and ventricles. Arch Pharm Res 1996. [DOI: 10.1007/bf02976382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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200
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Erichsen S, Zuo J, Curtis L, Rarey K, Hultcrantz M. Na,K-ATPase alpha- and beta-isoforms in the developing cochlea of the mouse. Hear Res 1996; 100:143-9. [PMID: 8922988 DOI: 10.1016/0378-5955(96)00105-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Immunohistochemistry was used to investigate the presence of Na,K-ATPase alpha- and beta-subunits isoforms (alpha 1, alpha 2, alpha 3, beta 1 and beta 2) in the cochlea of the mouse at different ages between embryological day (E) 19 and postnatal day (P) + 30. alpha 1 was mainly found in the stria vascularis and in the spiral ligament; it increased steadily from p+4. These data correlates well with the morphological and electrophysiological maturation of the cochlea. alpha 3 predominated in the spiral ganglia and the cochlear nerve. This finding is well in accordance with reports that alpha 3 seems to be associated with the nervous system. The beta-subunit was found mainly in those tissues where staining of the alpha-subunit also was seen. Both subunits were localized in tissue regions where fluid regulation is expected to play an important role. For some isoforms, the expression pattern of Na,K-ATPase during development in the mouse is different from that in the rat. The expression of Na,K-ATPase and that of glucocorticoid receptors during development in the inner ear of the mouse show a similar pattern, which may indicate that glucocorticoid receptors could be involved in regulating the expression of Na,K-ATPase.
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Affiliation(s)
- S Erichsen
- Department of Otorhinolaryngology, Karolinska Hospital, Stockholm, Sweden
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