Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Uvomorulin (E-cadherin), a cell adhesion molecule, and Na+,K(+)-adenosine triphosphatase (ATPase), a marker protein of the basal-lateral cell membrane domains of polarized epithelial cells, were investigated in a group of mouse skin tumors induced by a two-stage chemical carcinogenesis protocol and in cell lines derived from mouse skin papillomas and squamous cell carcinomas (SCC). Although these two markers were present in benign tumors and in nontumorigenic cell lines, the Na+,K(+)-ATPase showed an altered pattern of distribution that included the presence of enzyme not only in the basolateral domain but also on the apical domain of the cell membrane of basal and spinous cells in well-differentiated squamous cell carcinomas (SCC). In higher grade SCC, a loss of Na+,K(+)-ATPase immunoreactivity was simultaneously detected with a marginal or absent expression of uvomorulin. The more differentiated SCC and papillomas expressed less uvomorulin immunoreactivity than normal epidermal cells. Both markers were seen in tumor cell lines that produced well-differentiated SCC after subcutaneous inoculation into nude mice. Neither Na+,K(+)-ATPase nor uvomorulin could be detected in cell lines that produced high grade, poorly differentiated SCC. Northern blots confirmed the absence of uvomorulin mRNA in these highly malignant cell lines. These data indicate that progression from premalignant papilloma to low-grade SCC and subsequently to high-grade SCC is accompanied by loss of epithelial cell polarity as detected by changes in Na+,K(+)-ATPase and by decreased or absent expression of uvomorulin in tumors and cell lines characterized by an advanced malignant phenotype.
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PMID:Alterations in the expression of uvomorulin and Na+,K(+)-adenosine triphosphatase during mouse skin tumor progression. 131 85

Altered membrane polarity has been proposed as an important pathogenetic factor in the development of renal cysts in polycystic kidney disease. To determine whether this alteration in epithelial phenotype is a primary or secondary phenomenon, we examined the epithelial membrane polarity of SBM transgenic mice, in which epithelial proliferation mediated by the c-myc oncogene is an established primary event. Kidneys from 32 transgenic mice and 10 age-matched controls from fetal to adult age were immunostained with antibodies to Na,K-ATPase, fodrin, ankyrin, E-cadherin, and tubule segment-specific lectins. In normal control mice, Na,K-ATPase localization was apical in fetal kidneys but became translocated to the basolateral membrane at maturity. Early microcysts in fetal transgenic kidneys displayed similar (95 to 100%) apical Na,K-ATPase. In young and newborn transgenic mice (1 to 8 days of age), Na,K-ATPase localization was extremely heterogeneous. Noncystic tubules demonstrated either apical (mean 23 to 28%), basolateral (mean 48 to 58%), mixed (mean 4 to 15%), or absent (mean 10 to 13%) staining for Na,K-ATPase. Apical Na,K-ATPase was more frequently observed in early cysts (mean 55%) in young transgenic mice but became less prevalent in adult mice (mean 22%), where 30% of cysts had basolateral staining, 39% mixed patterns, and 9% absent staining. Macrocysts typically lost all Na,K-ATPase reactivity. At all ages, Na,K-ATPase colocalized well with cytoskeletal proteins ankyrin and fodrin. These heterogeneous patterns of Na,K-ATPase staining indicate that although altered cell polarity is frequent in early cystic epithelium of SBM mice, it is not a prerequisite to cystogenesis or progressive cyst enlargement. In conclusion, our results support the view that altered cystic membrane polarity is not a primary process, but represents the persistence of an immature epithelial phenotype characteristic of proliferative polycystic kidney disease epithelia.
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PMID:Analysis of the role of membrane polarity in polycystic kidney disease of transgenic SBM mice. 749 97

A primary function of cadherins is to regulate cell adhesion. Here, we demonstrate a broader function of cadherins in the differentiation of specialized epithelial cell phenotypes. In situ, the rat retinal pigment epithelium (RPE) forms cell-cell contacts within its monolayer, and at the apical membrane with the neural retina; Na+, K(+)-ATPase and the membrane cytoskeleton are restricted to the apical membrane. In vitro, RPE cells (RPE-J cell line) express an endogenous cadherin, form adherens junctions and a tight monolayer, but Na+,K(+)-ATPase is localized to both apical and basal-lateral membranes. Expression of E-cadherin in RPE-J cells results in restriction and accumulation of both Na+,K(+)-ATPase and the membrane cytoskeleton at the lateral membrane; these changes correlate with the synthesis of a different ankyrin isoform. In contrast to both RPE in situ and RPE-J cells that do not form desmosomes, E-cadherin expression in RPE-J cells induces accumulation of desmoglein mRNA, and assembly of desmosome-keratin complexes at cell-cell contacts. These results demonstrate that cadherins directly affect epithelial cell phenotype by remodeling the distributions of constitutively expressed proteins and by induced accumulation of specific proteins, which together lead to the generation of structurally and functionally distinct epithelial cell types.
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PMID:Plasticity in epithelial cell phenotype: modulation by expression of different cadherin cell adhesion molecules. 753 48

We have examined underlying causes for observations made in hepatocytes in which catalytic subunits of Na(+)-K(+)-ATPase are found both in bile canalicular (apical) and sinusoidal (basolateral) membrane domains, whereas functional activity is associated preferentially with sinusoidal membrane sites. In a series of parallel studies, we determined by both light and electron microscopy that Na(+)-K(+)-ATPase alpha-subunits were localized to both membrane domains of hepatocytes. With the use of purified liver plasma membrane subfractions, ouabain inhibition curves demonstrated similar inhibition constants (inhibition constant 10(-5) M), and immunoblots using alpha 1-, alpha 2-, and alpha 3-polyclonal and monoclonal antibodies demonstrated antigenic sites predominantly for alpha 1 in both membrane fractions. Also, Northern blot hybridization analysis revealed only the alpha 1-isoform in hepatocytes. In contrast to the bipolar distribution of the alpha 1-subunit, the beta-subunit was identified only at the sinusoidal surface using fluorescence labeling with a monoclonal antibody. The beta 1-isoform was demonstrated by Northern blot analysis and was present predominantly at the sinusoidal domain by immunoblotting with polyclonal antibodies. In addition to the bipolar distribution of alpha 1, immunoblotting of liver plasma membrane subfractions demonstrated a symmetrical distribution of fodrin, ankyrin, actin, and E-cadherin at both domains. These results suggest that functionally competent alpha/beta-complexes form at the sinusoidal domain, whereas only alpha 1-subunits are present at the apical pole.
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PMID:Hepatic Na(+)-K(+)-ATPase enzyme activity correlates with polarized beta-subunit expression. 763 61

We have studied mechanisms involved in generating a polarized distribution of Na/K-ATPase in the basal-lateral membrane of two clones of MDCK II cells. Both clones exhibit polarized distributions of marker proteins of the apical and basal-lateral membranes, including Na/K-ATPase, at steady state. Newly synthesized Na/K-ATPase, however, is delivered from the Golgi complex to both apical and basal-lateral membranes of one clone (II/J), and to the basal-lateral membrane of the other clone (II/G); Na/K-ATPase is selectively retained in the basal-lateral membrane resulting in the generation of complete cell surface polarity in both clones. Another basal-lateral membrane protein, E-cadherin, is sorted to the basal-lateral membrane in both MDCK clones, demonstrating that there is not a general sorting defect for basal-lateral membrane proteins in clone II/J cells. A glycosyl-phosphatidylinositol (GPI)-anchored protein (GP-2) and a glycosphingolipid (glucosylceramide, GlcCer) are preferentially transported to the apical membrane in clone II/G cells, but, in clone II/J cells, GP-2 and GlcCer are delivered equally to both apical and basal-lateral membranes, similar to Na/K-ATPase. To examine this apparent inter-relationship between sorting of GlcCer, GP-2 and Na/K-ATPase, sphingolipid synthesis was inhibited in clone II/G cells with the fungal metabolite, Fumonisin B1 (FB1). In the presence of FB1, GP-2 and Na/K-ATPase are delivered to both apical and basal-lateral membranes, similar to clone II/J cells; FB1 had no effect on sorting of E-cadherin to the basal-lateral membrane of II/G cells. Addition of exogenous ceramide, to circumvent the FB1 block, restored GP-2 and Na/K-ATPase sorting to the apical and basal-lateral membranes, respectively. These results show that the generation of complete cell surface polarity of Na/K-ATPase involves a hierarchy of sorting mechanisms in the Golgi complex and plasma membrane, and that Na/K-ATPase sorting in the Golgi complex of MDCK cells may be regulated by exclusion from an apical pathway(s). These results also provide new insights into sorting pathways for other apical and basal-lateral membrane proteins.
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PMID:Hierarchy of mechanisms involved in generating Na/K-ATPase polarity in MDCK epithelial cells. 765 95

The biogenesis of follicles from aggregates of precursor cells is an important morphogenetic process in thyroid embryology. It necessitates the creation of a polarized cell phenotype, assembly of specialized cell-cell junctions, and generation of follicular lumena. In this study we sought to investigate the relationship between cell polarization and lumen formation by studying the cell surface events that occurred when freshly isolated adult porcine thyroid cells reorganized to form follicles in primary culture. Follicular reorganization entailed the initial formation of solid three-dimensional cell aggregates and the subsequent appearance of lumena within aggregates. During the initial stage of cell aggregation, the adhesion molecule, E-cadherin, became expressed at all surfaces involved in cell-cell contact. Aggregation was inhibited by monoclonal antibodies that block cadherin function, indicating directly that E-cadherin is a dominant initial cell-cell adhesion molecule. Cell aggregation was also associated with the recruitment to the cell surface of ZO-1, a tight junction-associated protein, and Na+/K(+)-adenosine triphosphatase. These proteins were initially found throughout regions of cell-cell contact and only subsequently redistributed to their mature locations in tight junctions and the basolateral cell surface, respectively. In contrast, components associated with the apical membrane were first detected within large intracellular vacuoles, which subsequently fused with the cell surface between maturing tight junctions to yield the apical membrane domain and nascent follicular lumena. Follicle formation occurred independently of basal lamina assembly and TSH, although maintenance of follicular architecture required the presence of this hormone. These findings indicate that cultured follicles form in two distinct stages: 1) initial aggregation mediated by E-cadherin and associated with recruitment of components of both tight junctions and the basolateral membrane domain, and 2) subsequent formation of a specialized apical membrane domain by coordinated fusion of intracellular vacuoles at sites of the cell surface where tight junctions are maturing. We propose that follicular morphogenesis may arise as a consequence of epithelial cell polarization within coherent three-dimensional cell aggregates.
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PMID:Cadherin-mediated adhesion and apical membrane assembly define distinct steps during thyroid epithelial polarization and lumen formation. 766 88

MDCK and JTC cells were subjected to ATP depletion by treating the cells with 10 microM antimycin A and 10 mM 2-deoxyglucose. As visualized by confocal fluorescence microscopy, E-cadherin and Na+,K(+)-ATPase were rapidly internalized following depletion of the intracellular ATP stores. The time course of internalization was similar to the depolymerization of the cortical actin network and dissolution of the actin ring (see companion paper, this volume, pp. 3301-3313). Cell surface biotinylation was used to assay the amount of surface-accessible E-cadherin and Na+,K(+)-ATPase during ATP depletion. At 30 minutes of ATP depletion, 74% and 69% of E-cadherin and Na+,K(+)-ATPase were internalized, respectively, in MDCK cells. By 60 minutes of ATP depletion, internalization increased to 95% and 89%, respectively. The redistribution of both plasma membrane proteins was not microtubule dependent. Similar results were observed in JTC cells. Total biotinylated protein decreased by 67% and 82%, after 30 minutes and 60 minutes of ATP depletion, respectively. The E-cadherin internalization strongly suggests that disruption of adherens junctions occurred following ATP depletion. These results, along with the previously described loss of tight junction integrity, suggest that ATP depletion may be a useful method to study the assembly and disassembly of junctional complexes in epithelial cells.
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PMID:ATP depletion: a novel method to study junctional properties in epithelial tissues. II. Internalization of Na+,K(+)-ATPase and E-cadherin. 770 88

In the placenta the trophoblast cell layer separates maternal and fetal circulations and is involved in the active transport of selected substances across this barrier. We have used the JAR choriocarcinoma cell line to study aspects of trophoblast membrane transport. To determine whether JAR cells could be used in studies of vectorial transepithelial transport it was necessary to determine whether these cells were polarized and assembled tight junctions. In the present study we investigated JAR cells using a range of markers for specific cell surface domains combined with confocal laser scanning microscopy. Freshly isolated cells initially formed a confluent epithelial monolayer with recruitment of a tight junction-associated protein, ZO-1, and a cell adhesion molecule, E-cadherin, to the surface at sites of cell-cell contact. They did not, however, display cell surface polarization, as NaK-ATPase was not segregated in the basolateral domain, and a differentiated apical cell surface was not assembled. The monolayer stage was also unstable, as continued proliferation resulted in the formation of multilayered aggregates where ZO-1 and E-cadherin were lost from the cell surface. These results suggest that the JAR cell line is unlikely to be a suitable model for studies of transepithelial transport in the placenta.
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PMID:Characterization of cell polarity and epithelial junctions in the choriocarcinoma cell line, JAR. 771 26

Spectrin is a major structural protein associated with the cytoplasmic surface of plasma membranes of many types of cells. To study the functions of spectrin, we transfected Caco-2 intestinal epithelial cells with a plasmid conferring neomycin resistance and encoding either actin-binding or ankyrin-binding domains of beta G-spectrin fused with beta-galactosidase. These polypeptides, in principle, could interfere with the interaction of spectrin with actin or ankyrin, as well as block normal assembly of alpha- and beta-spectrin subunits. Cells expressing the fusion proteins represented only a small fraction of neomycin-resistant cells, but they could be detected based on expression of beta-galactosidase. Cells expressing spectrin domains exhibited a progressive decrease in amounts of endogenous beta G-spectrin, although alpha-spectrin was still present. Beta G-spectrin-deficient cells lost epithelial cell morphology, became multinucleated, and eventually disappeared after 10-14 d in culture. Spectrin-associated membrane proteins, ankyrin and adducin, as well as the Na+,K(+)-ATPase, which binds to ankyrin, exhibited altered distributions in cells transfected with beta G-spectrin domains. E-cadherin and F-actin, in contrast to ankyrin, adducin, and the Na+,K(+)-ATPase, were expressed, and they exhibited unaltered distribution in beta G-spectrin-deficient cells. Cells transfected with the same plasmid encoding beta-galactosidase alone survived in culture as the major population of neomycin-resistant cells, and they exhibited no change in morphology or in the distribution of spectrin-associated membrane proteins. These results establish that beta G-spectrin is essential for the normal morphology of epithelial cells, as well as for their maintenance in monolayer culture.
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PMID:Expression of functional domains of beta G-spectrin disrupts epithelial morphology in cultured cells. 789 72

To investigate the cellular mechanisms of ovarian epithelial carcinogenesis, a series of progressively transformed rat ovarian surface epithelial (ROSE) cell lines were developed and studied. Transfection of primary ROSE cells and an immortalized ROSE line (ROSE 199) with the pSV3neo plasmid (SV40 T-antigen) yielded transformed lines which retained epithelial morphology. In vivo selection of these pSV3neo cell populations resulted in further phenotypic transformation. Transfection of ROSE 199 with pSV2neo/c-H-rasEJ (rasEJp21) resulted in a malignant line which appeared fibroblast-like and formed invasive sarcomas both in athymic mice and in immunocompetent rats. Gap junctional intercellular communication (GJIC) and cell-cell adhesion were studied in this series of ROSE lines. Both c-H-rasEJ-transformation and in vivo selection resulted in a significant reduction of GJIC between adjoining cells and a transition of in vitro migration as continuous epithelial sheets to the dissociation of individual cells. This apparent shift in cell adhesiveness was associated with reduced expression of the E-cadherin adhesion molecule. Our data suggest that neoplastic progression of the ovarian surface epithelium may be associated with concomitant reductions in GJIC, E-cadherin expression and functional adhesiveness.
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PMID:An in vitro model of ovarian epithelial carcinogenesis: changes in cell-cell communication and adhesion occurring during neoplastic progression. 832 8


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