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  • Proceedings of the National Academy of Sciences  (11)
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  • Proceedings of the National Academy of Sciences  (11)
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  • 1
    Online Resource
    Online Resource
    Structure of murine and human renal type II Na+-phosphate cotransporter genes (Npt2 and NPT2).
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 14 ( 1996-07-09), p. 7409-7414
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 14 ( 1996-07-09), p. 7409-7414
    Abstract: Na+-phosphate (Pi) cotransport across the renal brush border membrane is the rate limiting step in the overall reabsorption of filtered Pi. Murine and human renal-specific cDNAs (NaPi-7 and NaPi-3, respectively) related to this cotransporter activity (type II Na+-Pi cotransporter) have been cloned. We now report the cloning and characterization of the corresponding mouse (Npt2) and human (NPT2) genes. The genes were cloned by screening mouse genomic and human chromosome 5-specific libraries, respectively. Both genes are approximately 16 kb and are comprised of 13 exons and 12 introns, the junctions of which conform to donor and acceptor site consensus sequences. Putative CAAT and TATA boxes are located, respectively, at positions -147 and -40 of the Npt2 gene and -143 and -51 of the NPT2 gene, relative to nucleotide 1 of the corresponding cDNAs. The translation initiation site is within exon 2 of both genes. The first 220 bp of the mouse and human promoter regions exhibit 72% identity. Two transcription start sites (at positions -9 and - 10 with respect to nucleotide 1 of NaPi-7 cDNA) and two polyadenylylation signals were identified in the Npt2 gene by primer extension, 5' and 3' rapid amplification of cDNA ends (RACE). A 484-bp 5' flanking region of the Npt2 gene, comprising the CAAT box, TATA box, and exon 1, was cloned upstream of a luciferase reporter gene; this construct significantly stimulated luciferase gene expression, relative to controls, when transiently transfected into OK cells, a renal cell line expressing type II Na+ -Pi cotransporter activity. The present data provide a basis for detailed analysis of cis and trans elements involved in the regulation of Npt2/NPT2 gene transcription and facilitate screening for mutations in the NPT2 gene in patients with autosomally inherited disorders of renal Pi reabsorption.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.14.7409
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    Expression cloning and functional characterization of the kidney cortex high-affinity proton-coupled peptide transporter.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 1 ( 1996-01-09), p. 284-289
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 1 ( 1996-01-09), p. 284-289
    Abstract: The presence of a proton-coupled electrogenic high-affinity peptide transporter in the apical membrane of tubular cells has been demonstrated by microperfusion studies and by use of brush border membrane vesicles. The transporter mediates tubular uptake of filtered di- and tripeptides and aminocephalosporin antibiotics. We have used expression cloning in Xenopus laevis oocytes for identification and characterization of the renal high-affinity peptide transporter. Injection of poly(A)+ RNA isolated from rabbit kidney cortex into oocytes resulted in expression of a pH-dependent transport activity for the aminocephalosporin antibiotic cefadroxil. After size fractionation of poly(A)+ RNA the transport activity was identified in the 3.0- to 5.0-kb fractions, which were used for construction of a cDNA library. The library was screened for expression of cefadroxil transport after injection of complementary RNA synthesized in vitro from different pools of clones. A single clone (rPepT2) was isolated that stimulated cefadroxil uptake into oocytes approximately 70-fold at a pH of 6.0. Kinetic analysis of cefadroxil uptake expressed by the transporter's complementary RNA showed a single saturable high-affinity transport system shared by dipeptides, tripeptides, and selected amino-beta-lactam antibiotics. Electrophysiological studies established that the transport activity is electrogenic and affected by membrane potential. Sequencing of the cDNA predicts a protein of 729 amino acids with 12 membrane-spanning domains. Although there is a significant amino acid sequence identity (47%) to the recently cloned peptide transporters from rabbit and human small intestine, the renal transporter shows distinct structural and functional differences.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.1.284
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    Cloning and expression of cDNA for a Na/Pi cotransport system of kidney cortex.
    Proceedings of the National Academy of Sciences ; 1991
    In:  Proceedings of the National Academy of Sciences Vol. 88, No. 21 ( 1991-11), p. 9608-9612
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 88, No. 21 ( 1991-11), p. 9608-9612
    Abstract: A cDNA library from rabbit kidney cortex was screened for expression of Na-dependent transport of phosphate (Pi) using Xenopus laevis oocytes as an expression system. A single clone was eventually isolated (designated NaPi-1) that stimulated expression of Na/Pi cotransport approximately 700-fold compared to total mRNA. The predicted sequence of the Na/Pi cotransporter consists of 465 amino acids (relative molecular mass, 51,797); hydropathy profile predictions suggest six (possibly eight) membrane-spanning segments. In vitro translation of NaPi-1/complementary RNA in the presence of pancreatic microsomes indicated NaPi-1 to be a glycosylated protein; four potential N-glycosylation sites are present in the amino acid sequence. Northern blot analysis demonstrated the presence of NaPi-1/mRNA in kidney cortex and liver; no hybridization signal was obtained with mRNA from other tissues (including small intestine). Kinetic analysis of Na/Pi cotransport expressed by NaPi-1/complementary RNA demonstrated characteristics (sodium interaction) similar to those observed in cortical apical membranes. The alignment of 5 amino acid residues (Gly342/Ala381-Xaa-Xaa-Xaa-Xaa-Leu386-Xaa-Xaa-Xaa-P ro390- Arg391) is consistent with a motif proposed for Na-dependent transport systems. We conclude that we have cloned a cDNA for a Na/Pi cotransport system present in rabbit kidney cortex.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.88.21.9608
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1991
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Stimulation of system y(+)-like amino acid transport by the heavy chain of human 4F2 surface antigen in Xenopus laevis oocytes.
    Proceedings of the National Academy of Sciences ; 1992
    In:  Proceedings of the National Academy of Sciences Vol. 89, No. 12 ( 1992-06-15), p. 5606-5610
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 89, No. 12 ( 1992-06-15), p. 5606-5610
    Abstract: A kidney cortex cDNA clone (rBAT) has recently been isolated, which upon in vitro transcription and capping complementary RNA (cRNA) and injection into Xenopus laevis oocytes induces a system b0,(+)-like amino acid transport activity. This cDNA encodes a type II membrane glycoprotein that shows significant homology to another type II membrane glycoprotein, the heavy chain of the human and mouse 4F2 surface antigen (4F2hc). Here we demonstrate that injection of human 4F2hc cRNA into oocytes results in the activation of a cation-preferring amino acid transport system that appears to be identical to the y(+)-like transport already present in the oocyte. This is based on the following results: (i) Injection of in vitro transcripts from 4F2hc cDNA (4F2hc cRNA) into oocytes stimulates up to 10-fold the sodium-independent uptake of L-arginine and up to 4.1-fold the sodium-dependent uptake of L-leucine. In contrast, 4F2hc cRNA does not increase the basal sodium-independent uptake of L-leucine. (ii) Basal and 4F2hc cRNA-stimulated sodium-independent uptake of L-arginine is completely inhibited by L-leucine in the presence of sodium. Similarly, the basal and 4F2hc cRNA-stimulated sodium-dependent uptake of L-leucine is entirely inhibited by L-arginine. (iii) The stimulation of sodium-independent uptake of L-arginine and the stimulation of sodium-dependent uptake of L-leucine induced by injection of 4F2hc cRNA are both completely inhibited by dibasic L amino acids and to a lesser extent by D-ornithine. (iv) Both basal and 4F2hc cRNA-stimulated sodium-independent uptake of L-arginine show two additional characteristics of the system y+ transport activity: inhibition of L-arginine uptake by L-homoserine only in the presence of sodium and an increase in the inhibition exerted by L-histidine as the extracellular pH decreased. Our results allow us to propose that an additional family of type II membrane glycoproteins (composed by rBAT and 4F2hc) is involved in amino acid transport, either as specific activators or as components of amino acid transport systems.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.89.12.5606
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1992
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Expression cloning of human and rat renal cortex Na/Pi cotransport.
    Proceedings of the National Academy of Sciences ; 1993
    In:  Proceedings of the National Academy of Sciences Vol. 90, No. 13 ( 1993-07), p. 5979-5983
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 90, No. 13 ( 1993-07), p. 5979-5983
    Abstract: We have isolated two cDNA clones, NaPi-2 and NaPi-3, by screening rat kidney cortex and human kidney cortex cDNA libraries, respectively, for expression of sodium-dependent phosphate transport in Xenopus laevis oocytes. Substrate specificity and a detailed kinetic analysis (Na, Pi, H+ concentrations) suggested that expressed uptake activities relate to proximal tubular brush border membrane Na/Pi cotransport. NaPi-2 cDNA contains 2464 bp encoding a protein of 637 aa; NaPi-3 cDNA contains 2573 bp encoding a protein of 639 aa. NaPi-2- and NaPi-3-deduced protein sequences show high homology to each other but are different from the protein sequence deduced from the previously cloned NaPi-1 cDNA (from rabbit proximal tubules). Hydropathy profile predictions suggest at least eight membrane-spanning regions in NaPi-2/3-related proteins. In vitro translation results in proteins of the expected size and suggests glycosylation. Northern blot analysis shows corresponding mRNA species (approximately 2.7 kb) in kidney cortex of various species but no hybridization with RNAs isolated from a variety of other tissues (including intestinal segments); a hybridization signal (approximately 4.8 kb) was observed only in the lung (human). We conclude that we have structurally identified two closely related proteins most likely involved in human and rat renal brush border Na/Pi cotransport.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.90.13.5979
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1993
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 6
    Online Resource
    Online Resource
    Expression of a renal type I sodium/phosphate transporter (NaPi-1) induces a conductance in Xenopus oocytes permeable for organic and inorganic anions.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 11 ( 1996-05-28), p. 5347-5351
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 11 ( 1996-05-28), p. 5347-5351
    Abstract: Two distinct molecular types (I and II) of renal proximal tubular brush border Na+/Pi cotransporters have been identified by expression cloning on the basis of their capacity to induce Na+-dependent Pi influx in tracer experiments. Whereas the type II transporters (e.g., NaPi-2 and NaPi-3) resemble well known characteristics of brush border Na+/Pi cotransport, little is known about the properties of the type I transporter (NaPi-1). In contrast to type II, type I transporters produced electrogenic transport only at high extracellular Pi concentrations ( 〉 or =3 mM). On the other hand, expression of NaPi-1 induced a Cl- conductance in Xenopus laevis oocytes, which was inhibited by Cl- channel blockers [5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) 〉 niflumic acid 〉 〉 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid]. Further, the Cl- conductance was inhibited by the organic anions phenol red, benzylpenicillin (penicillin G), and probenecid. These organic anions induced outwardly directed currents in the absence of Cl-. In tracer studies, we observed uptake of benzylpenicillin with a Km of 0.22 mM; benzylpenicillin uptake was inhibited by NPPB and niflumic acid. These findings suggest that the type I Na+/Pi cotransporter functions also as a novel type of anion channel permeable not only for Cl- but also for organic anions. Such an apical anion channel could serve an important role in the transport of Cl- and the excretion of anionic xenobiotics.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.11.5347
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    Expression cloning of rat renal Na+/SO4(2-) cotransport.
    Proceedings of the National Academy of Sciences ; 1993
    In:  Proceedings of the National Academy of Sciences Vol. 90, No. 17 ( 1993-09), p. 8073-8077
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 90, No. 17 ( 1993-09), p. 8073-8077
    Abstract: Injection of rat kidney cortex mRNA into Xenopus laevis oocytes leads to a stimulation of Na(+)-dependent SO4(2-) uptake. Based on this information, we have isolated from a corresponding library a cDNA (NaSi-1) that is most likely related to a Na+/SO4(2-) cotransport system. NaSi-1 cRNA leads in a time- and dose-dependent manner to specific stimulation of Na(+)-dependent SO4(2-) uptake in oocytes. The apparent affinity constants of the NaSi-1 cRNA-expressed transport resemble those of Na+/SO4(2-) cotransport in brush-border membrane. The NaSi-1 cDNA contains 2239 bp [including a poly(A) tail] and encodes a protein of 595 amino acids (66.05 kDa); the hydropathy profile suggests at least eight membrane-spanning regions. In vitro translation of NaSi-1 cRNA results in a protein of the expected size and suggests glycosylation. Northern blot analysis shows signals of 2.3 and 2.9 kb in kidney (more abundant in cortex than in papilla/medulla) and in mucosa of small intestine of rats. The above data indicate that we have structurally identified a membrane protein involved in renal and small-intestinal brush-border membrane Na+/SO4(2-) cotransport.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.90.17.8073
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1993
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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  • 8
    Online Resource
    Online Resource
    Demonstration of Electrogenic Na + -dependent D-glucose Transport in Intestinal Brush Border Membranes
    Proceedings of the National Academy of Sciences ; 1974
    In:  Proceedings of the National Academy of Sciences Vol. 71, No. 2 ( 1974-02), p. 484-488
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 71, No. 2 ( 1974-02), p. 484-488
    Abstract: Na + -coupled D-glucose transport was studied in isolated membrane vesicles from intestinal brush borders. Concentration gradients of SCN - , K + , and H + were established between the intravesicular solution and the incubation medium and their influence on D-glucose uptake from the medium was measured. A gradient (medium 〉 vesicle) of NaSCN, but not of KSCN, produced a transient overshoot of D-glucose uptake above the equilibrium level. Similarly, an increase of the membrane conductance with valinomycin (K + -conductance) or with uncoupling agents of oxidative phosphorylation (H + -conductance) induced an overshooting D-glucose uptake, provided a (vesicle 〉 medium) K + -gradient or a H + -gradient, respectively, was present in each case. The transient overshoot is evidence that D-glucose was taken up against its concentration gradient (up to 10-fold). The gradients of SCN - , K + (in the presence of valinomycin), and H + (in the presence of uncouplers) are thought to contribute to the “driving” force for this “active” D-glucose transport by changing the electrical potential across the vesicle membrane and thus making the inside more negative (with respect to the medium). These experiments, therefore, provide evidence that the Na + -coupled D-glucose translocation across the brush border membrane is an electrogenic process, i.e., the positive charge associated with Na + is not compensated by the co-movement of an anion or the counter-movement of a cation via the glucose “carrier”. The results imply that an electrical potential across the brush border membrane may play an important role in determining the transport of D-glucose by intact cells.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.71.2.484
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1974
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 9
    Online Resource
    Online Resource
    Expression cloning of a cDNA from rabbit kidney cortex that induces a single transport system for cystine and dibasic and neutral amino acids.
    Proceedings of the National Academy of Sciences ; 1992
    In:  Proceedings of the National Academy of Sciences Vol. 89, No. 12 ( 1992-06-15), p. 5601-5605
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 89, No. 12 ( 1992-06-15), p. 5601-5605
    Abstract: We have isolated a cDNA clone by screening a rabbit kidney cortex cDNA library for expression of sodium-independent transport of L-arginine and L-alanine in Xenopus laevis oocytes. Expressed uptake relates to a single component of sodium-independent transport for dibasic and neutral amino acids. This transport activity resembles the functionally defined system b0,+ and carries cystine and dibasic amino acids with high affinity. The rBAT (b0,+ amino acid transporter-related) mRNA is found mainly in kidney and intestinal mucosa. It encodes a predicted 77.8-kDa protein with only one putative transmembrane domain and seven potential N-glycosylation sites. This protein could either be a constitutive element or a specific activator of system b0,+.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.89.12.5601
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1992
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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  • 10
    Online Resource
    Online Resource
    In vivo suppression of the renal Na+/Pi cotransporter by antisense oligonucleotides.
    Proceedings of the National Academy of Sciences ; 1996
    In:  Proceedings of the National Academy of Sciences Vol. 93, No. 10 ( 1996-05-14), p. 4903-4906
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 93, No. 10 ( 1996-05-14), p. 4903-4906
    Abstract: A 20-mer phosphorothioate oligonucleotide (AS1) was designed to hybridize to the message for the rat kidney sodium phosphate cotransporter NaPi-2 close to the translation initiation site. Single intravenous doses of this oligonucleotide were given to rats maintained on a low phosphorus diet to increase NaPi-2 expression. At 3 days after oligonucleotide infusion, rats receiving 2.5 micromol of AS1 exhibited a reduction in renal NaPi-2 to cyclophilin mRNA ratio by 40% +/- 17%, and rats receiving 7.5 micromol of AS1 exhibited a reduction in NaPi-2 to cyclophilin mRNA ratio by 46% +/- 21%. Reversed-sequence AS1 was without effect. The higher dose of 7.5 micromol of AS1 also reduced the rate of phosphate uptake into renal brush border membrane vesicles and the expression of NaPi-2 protein detected by Western blotting in these vesicles. Reversed sequence AS1 was again without effect on these parameters. These results suggest that systemically infused oligonucleotides can exert antisense effects in the renal proximal tubule.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.93.10.4903
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1996
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
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