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Hinze C, Karaiskos N, Boltengagen A, Walentin K, Redo K, Himmerkus N, Bleich M, Potter SS, Potter AS, Eckardt KU, Kocks C, Rajewsky N, Schmidt-Ott KM. Kidney Single-cell Transcriptomes Predict Spatial Corticomedullary Gene Expression and Tissue Osmolality Gradients. J Am Soc Nephrol 2021; 32:291-306. [PMID: 33239393 PMCID: PMC8054904 DOI: 10.1681/asn.2020070930] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 10/15/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Single-cell transcriptomes from dissociated tissues provide insights into cell types and their gene expression and may harbor additional information on spatial position and the local microenvironment. The kidney's cells are embedded into a gradient of increasing tissue osmolality from the cortex to the medulla, which may alter their transcriptomes and provide cues for spatial reconstruction. METHODS Single-cell or single-nuclei mRNA sequencing of dissociated mouse kidneys and of dissected cortex, outer, and inner medulla, to represent the corticomedullary axis, was performed. Computational approaches predicted the spatial ordering of cells along the corticomedullary axis and quantitated expression levels of osmo-responsive genes. In situ hybridization validated computational predictions of spatial gene-expression patterns. The strategy was used to compare single-cell transcriptomes from wild-type mice to those of mice with a collecting duct-specific knockout of the transcription factor grainyhead-like 2 (Grhl2CD-/-), which display reduced renal medullary osmolality. RESULTS Single-cell transcriptomics from dissociated kidneys provided sufficient information to approximately reconstruct the spatial position of kidney tubule cells and to predict corticomedullary gene expression. Spatial gene expression in the kidney changes gradually and osmo-responsive genes follow the physiologic corticomedullary gradient of tissue osmolality. Single-nuclei transcriptomes from Grhl2CD-/- mice indicated a flattened expression gradient of osmo-responsive genes compared with control mice, consistent with their physiologic phenotype. CONCLUSIONS Single-cell transcriptomics from dissociated kidneys facilitated the prediction of spatial gene expression along the corticomedullary axis and quantitation of osmotically regulated genes, allowing the prediction of a physiologic phenotype.
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Affiliation(s)
- Christian Hinze
- Department of Nephrology and Medical Intensive Care, Charité – Universitätsmedizin, Berlin, Germany,Molecular and Translational Kidney Research, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany,Berlin Institute of Health, Berlin, Germany
| | - Nikos Karaiskos
- Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Anastasiya Boltengagen
- Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Katharina Walentin
- Molecular and Translational Kidney Research, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Klea Redo
- Department of Nephrology and Medical Intensive Care, Charité – Universitätsmedizin, Berlin, Germany,Molecular and Translational Kidney Research, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Nina Himmerkus
- Department of Physiology, Physiology of Membrane Transport, Christian-Albrechts-Universität, Kiel, Germany
| | - Markus Bleich
- Department of Physiology, Physiology of Membrane Transport, Christian-Albrechts-Universität, Kiel, Germany
| | - S. Steven Potter
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio
| | - Andrew S. Potter
- Division of Developmental Biology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio
| | - Kai-Uwe Eckardt
- Department of Nephrology and Medical Intensive Care, Charité – Universitätsmedizin, Berlin, Germany
| | - Christine Kocks
- Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Nikolaus Rajewsky
- Systems Biology of Gene Regulatory Elements, Berlin Institute for Medical Systems Biology, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Kai M. Schmidt-Ott
- Department of Nephrology and Medical Intensive Care, Charité – Universitätsmedizin, Berlin, Germany,Molecular and Translational Kidney Research, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany,Berlin Institute of Health, Berlin, Germany
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2
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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3
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Protein mediated regulation of the NHE1 isoform of the Na + /H + exchanger in renal cells. A regulatory role of Hsp90 and AKT kinase. Cell Signal 2017; 36:145-153. [DOI: 10.1016/j.cellsig.2017.05.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 04/28/2017] [Accepted: 05/05/2017] [Indexed: 11/19/2022]
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4
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Odunewu A, Fliegel L. Acidosis-mediated regulation of the NHE1 isoform of the Na⁺/H⁺ exchanger in renal cells. Am J Physiol Renal Physiol 2013; 305:F370-81. [PMID: 23678047 DOI: 10.1152/ajprenal.00598.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The mammalian Na⁺/H⁺ exchanger isoform 1 (NHE1) is a ubiquitous plasma membrane protein that regulates intracellular pH by removing a proton in exchange for extracellular sodium. Renal tissues are subject to metabolic and respiratory acidosis, and acidosis has been shown to acutely activate NHE1 activity in other cell types. We examined if NHE1 is activated by acute acidosis in HEK293 and Madin-Darby canine kidney (MDCK) cells. Acute sustained intracellular acidosis (SIA) activated NHE1 in both cell types. We expressed wild-type and mutant NHE1 cDNAs in MDCK cells. All the cDNAs had a L163F/G174S mutation, which conferred a 100-fold resistance to EMD87580, an NHE1-specific inhibitor. We assayed exogenous NHE1 activity while inhibiting endogenous activity with EMD87580 and while inhibiting the NHE3 isoform of the Na⁺/H⁺ exchanger using the isoform-specific inhibitor S3226. We examined the activation and phosphorylation of the wild-type and mutant NHE1 proteins in response to SIA. In MDCK cells we demonstrated that the amino acids Ser⁷⁷¹, Ser⁷⁷⁶, Thr⁷⁷⁹, and Ser⁷⁸⁵ are important for NHE1 phosphorylation and activation after acute SIA. SIA activated ERK-dependent pathways in MDCK cells, and this was blocked by treatment with the MEK inhibitor U0126. Treatment with U0126 also blocked activation of NHE1 by SIA. These results suggest that acute acidosis activates NHE1 in mammalian kidney cells and that in MDCK cells this activation occurs through an ERK-dependent pathway affecting phosphorylation of a distinct set of amino acids in the cytosolic regulatory tail of NHE1.
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Affiliation(s)
- Ayodeji Odunewu
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
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5
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Fenton RA, Praetorius J. Molecular Physiology of the Medullary Collecting Duct. Compr Physiol 2011; 1:1031-56. [DOI: 10.1002/cphy.c100064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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6
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Abstract
NHE3 is the brush-border (BB) Na+/H+exchanger of small intestine, colon, and renal proximal tubule which is involved in large amounts of neutral Na+absorption. NHE3 is a highly regulated transporter, being both stimulated and inhibited by signaling that mimics the postprandial state. It also undergoes downregulation in diarrheal diseases as well as changes in renal disorders. For this regulation, NHE3 exists in large, multiprotein complexes in which it associates with at least nine other proteins. This review deals with short-term regulation of NHE3 and the identity and function of its recognized interacting partners and the multiprotein complexes in which NHE3 functions.
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Affiliation(s)
- Mark Donowitz
- Department of Medicine, GI Division, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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7
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Flegelova H, Sychrova H. Mammalian NHE2 Na+/H+exchanger mediates efflux of potassium upon heterologous expression in yeast. FEBS Lett 2005; 579:4733-8. [PMID: 16098519 DOI: 10.1016/j.febslet.2005.07.046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2005] [Revised: 07/18/2005] [Accepted: 07/19/2005] [Indexed: 11/29/2022]
Abstract
Na(+)/H+exchangers form a broad family of transporters that mediate opposing fluxes of alkali metal cations and protons across cell membranes. They play multiple roles in different organisms (protection from toxic cations, regulation of cell volume or pH). Rat NHE2 exchanger was expressed in a Saccharomyces cerevisiae mutant strain lacking its own exporters of alkali metal cations. Though most of the overexpressed NHE2 remained entrapped in the secretory pathway, part of it reached the plasma membrane and mediated K+ efflux from the yeast. We demonstrate for the first time that a mammalian Na(+)/H+ exchanger transports alkali metal cations in yeast in the opposite direction than in mammalian cells, and that the substrate specificity of the rat NHE2 exchanger is limited only to potassium cations upon expression in yeast cells.
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Affiliation(s)
- Hana Flegelova
- Department of Membrane Transport, Institute of Physiology AS CR, Videnska 1083, 142 20 Prague 4, Czech Republic
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8
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Abstract
The countercurrent system in the medulla of the mammalian kidney provides the basis for the production of urine of widely varying osmolalities, but necessarily entails extreme conditions for medullary cells, i.e., high concentrations of solutes (mainly NaCl and urea) in antidiuresis, massive changes in extracellular solute concentrations during the transitions from antidiuresis to diuresis and vice versa, and low oxygen tension. The strategies used by medullary cells to survive in this hostile milieu include accumulation of organic osmolytes and heat shock proteins, the extensive use of the glycolysis for energy production, and a well-orchestrated network of signaling pathways coordinating medullary circulation and tubular work.
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Affiliation(s)
- Wolfgang Neuhofer
- Department of Physiology, University of Munich, D-80336 Munich, Germany.
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9
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Wagner CA, Lükewille U, Valles P, Breton S, Brown D, Giebisch GH, Geibel JP. A rapid enzymatic method for the isolation of defined kidney tubule fragments from mouse. Pflugers Arch 2003; 446:623-32. [PMID: 12748863 DOI: 10.1007/s00424-003-1082-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2002] [Accepted: 03/31/2003] [Indexed: 10/26/2022]
Abstract
The increasing number of available genetically manipulated mice makes it necessary to develop tools and techniques for examining the phenotypes of these animals. We have developed a straightforward and rapid method for the isolation of large quantities of single tubule fragments from the mouse kidney. Immunohistochemistry, electron microscopy, and fluorescence microscopy were used to evaluate the viability, functional characteristics, and morphology of proximal tubules (PT), and collecting ducts from cortex (CCD) and inner stripe of the outer medulla (ISOMCD). Tubules were isolated using a modified collagenase digestion technique, and selected under light microscopy for experimentation. Electron microscopy and trypan blue exclusion showed that a large portion of unselected proximal tubules were damaged by the digestion procedure. The selected tubules, however, all excluded trypan blue, indicating that the plasma membrane had remained intact. Immunocytochemistry on isolated CCD showed normal distribution of H(+)-ATPase, pendrin, and anion exchanger-1 (AE-1) staining. The pH-sensitive dye 2',7'-bis(2-carboxylethyl)-5(6)-carboxyfluorescein (BCECF) was used to measure Na(+)-dependent and -independent intracellular pH (pH(i)) recovery rates in PT, and in single intercalated cells of CCD and ISOMCD fragments. Na(+)-dependent pH(i)-recovery was 0.144+/-0.008 (PT), 0.182+/-0.013 (CCD), and 0.112+/-0.010 pH units/min. (ISOMCD). Na(+)-independent pH(i) recovery was found in all three segments (PT: 0.021+/-0.002, CCD: 0.037+/-0.002, ISOMCD: 0.033+/-0.002 pH units/min) and was sensitive to concanamycin. In summary, we have developed a new technique for rapid and straightforward preparation of large quantities of defined tubule fragments from mouse kidney. Using this technique, the first measurements of plasma membrane vacuolar H(+)-ATPase activities in mouse PT and collecting duct were made. This technique will facilitate further characterization of kidney function in normal and genetically manipulated animals.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
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10
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Wang XF, Yu MK, Lam SY, Leung KM, Jiang JL, Leung PS, Ko WH, Leung PY, Chew SBC, Liu CQ, Tse CM, Chan HC. Expression, immunolocalization, and functional activity of Na+/H+ exchanger isoforms in mouse endometrial epithelium. Biol Reprod 2003; 68:302-8. [PMID: 12493726 DOI: 10.1095/biolreprod.102.005645] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The luminal fluid microenvironment of the uterus is important for sperm capacitation and embryo development. In an attempt to understand the possible role of Na(+)/H(+) exchangers (NHEs) in uterine function, the mRNAs of different NHE isoforms as well as their subcellular localization (apical versus basolateral) and functional activity were investigated in mouse endometrial epithelial cells using reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry, and intracellular pH (pH(i)) measurement techniques. The presence of NHE1, NHE2, and NHE4, but not NHE3 mRNAs were revealed by RT-PCR. Immunostaining showed that NHE1, NHE2, and NHE4 were present in both apical and basolateral membranes. The pH(i) recovery from intracellular acidification was Na(+)-dependent; however, the rate of pH(i) recovery depending on basolateral Na(+) was 12.4 times faster than that depending on apical Na(+). The Na(+)-dependent rate of pH(i) recovery was also inhibited by amiloride, indicating H(+) extrusion through NHEs; however, the amiloride sensitivity of the apical membrane was less than that of the basolateral membrane, suggesting the involvement of different types of NHEs in the two membranes. The results indicate that the basolaterally located NHE1, NHE2, and NHE4, in addition to participating in the homeostatic control of intracellular pH, may play a role in H(+) extrusion in order to achieve transepithelial HCO(3)(-) secretion. The apically located NHEs may be involved in mediating Na(+) absorption as alternatives of or complementary to epithelial Na(+) channels.
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Affiliation(s)
- X F Wang
- Department of Physiology, The Chinese University of Hong Kong, Shatin, China
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11
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Hill C, Giesberts AN, White SJ. Expression of isoforms of the Na(+)/H(+) exchanger in M-1 mouse cortical collecting duct cells. Am J Physiol Renal Physiol 2002; 282:F649-54. [PMID: 11880326 DOI: 10.1152/ajprenal.00291.2000] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Na(+)/H(+) exchanger (NHE) proteins perform a variety of functions in the kidney and are differentially distributed among nephron segments. The purpose of this study was to identify NHE isoforms in murine M-1 cells as a model of cortical collecting duct principal cells. It was found that mRNAs corresponding to NHE1, NHE2, and NHE4 are expressed in M-1 cells. NHE-dependent regulation of intracellular pH (pH(i)) was investigated in the absence of extracellular HCO. Application of a 20 mM NH(4)Cl pulse resulted in a reversible intracellular acidification from which recovery was partially inhibited by application of 1 mM amiloride to either the apical or the basolateral membranes and was abolished when amiloride was applied to both sides of the monolayers, which suggests that NHEs are expressed in both the apical and the basolateral cell membranes of M-1 cells. The purinergic agonists ATP and benzoylbenzoyl-ATP caused a reduction of pH(i) when applied to the apical membrane, which suggests pH(i) may be influenced by extracellular nucleotides in the luminal fluid of the cortical collecting duct.
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Affiliation(s)
- C Hill
- Department of Biomedical Science, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom
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12
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Cavet ME, Akhter S, Murtazina R, Sanchez de Medina F, Tse CM, Donowitz M. Half-lives of plasma membrane Na(+)/H(+) exchangers NHE1-3: plasma membrane NHE2 has a rapid rate of degradation. Am J Physiol Cell Physiol 2001; 281:C2039-48. [PMID: 11698263 DOI: 10.1152/ajpcell.2001.281.6.c2039] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Na(+)/H(+) exchangers NHE2 and NHE3 are involved in epithelial Na(+) and HCO absorption. To increase insights into the functions of NHE2 vs. NHE3, we compared their cellular processing with each other and with the housekeeping isoform NHE1. Using biotinylated exchanger, we determined that the half-life of plasma membrane NHE2 was short (3 h) compared with that of NHE1 (24 h) and NHE3 (14 h) in both PS120 fibroblasts and Caco-2 cells. NHE2 transport and plasma membrane levels were reduced by 3 h of Brefeldin A treatment, whereas NHE1 was unaffected. NHE2 was degraded by the lysosomes but not proteosomes, as demonstrated by increasing levels of endocytosed NHE2 protein after inhibition of the lysosomes, but not with proteosome inhibition. Unlike that of NHE3, basal NHE2 transport activity was not affected by phosphatidylinositol 3-kinase inhibition and did not appear to be localized in the juxtanuclear recycling endosome. Therefore, for NHE2, protein degradation and/or protein synthesis probably play important roles in its basal and regulated states. These results suggest fundamental differences in the cellular processing and trafficking of NHE2 and NHE3. These differences may underlie the specialized roles that these exchangers play in epithelial cells.
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Affiliation(s)
- M E Cavet
- Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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13
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Mukhin YV, Vlasova T, Jaffa AA, Collinsworth G, Bell JL, Tholanikunnel BG, Pettus T, Fitzgibbon W, Ploth DW, Raymond JR, Garnovskaya MN. Bradykinin B2 receptors activate Na+/H+ exchange in mIMCD-3 cells via Janus kinase 2 and Ca2+/calmodulin. J Biol Chem 2001; 276:17339-46. [PMID: 11278760 DOI: 10.1074/jbc.m010834200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We used a cultured murine cell model of the inner medullary collecting duct (mIMCD-3 cells) to examine the regulation of the ubiquitous sodium-proton exchanger, Na+/H+ exchanger isoform 1 (NHE-1), by a prototypical G protein-coupled receptor, the bradykinin B2 receptor. Bradykinin rapidly activates NHE-1 in a concentration-dependent manner as assessed by proton microphysiometry of quiescent cells and by 2'-7'-bis[2-carboxymethyl]-5(6)-carboxyfluorescein fluorescence measuring the accelerated rate of pH(i) recovery from an imposed acid load. The activation of NHE-1 is blocked by inhibitors of the bradykinin B2 receptor, phospholipase C, Ca2+/calmodulin (CaM), and Janus kinase 2 (Jak2), but not by pertussis toxin or by inhibitors of protein kinase C and phosphatidylinositol 3'-kinase. Immunoprecipitation studies showed that bradykinin stimulates the assembly of a signal transduction complex that includes CaM, Jak2, and NHE-1. CaM appears to be a direct substrate for phosphorylation by Jak2 as measured by an in vitro kinase assay. We propose that Jak2 is a new indirect regulator of NHE-1 activity, which modulates the activity of NHE-1 by increasing the tyrosine phosphorylation of CaM and most likely by increasing the binding of CaM to NHE-1.
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Affiliation(s)
- Y V Mukhin
- Medical and Research Services of the Ralph H. Johnson Veterans Affairs Medical Center, and Department of Medicine of the Medical University of South Carolina, Charleston, South Carolina 29425, USA
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14
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Leung GP, Tse CM, Chew SB, Wong PY. Expression of multiple Na+/H+ exchanger isoforms in cultured epithelial cells from rat efferent duct and cauda epididymidis. Biol Reprod 2001; 64:482-90. [PMID: 11159350 DOI: 10.1095/biolreprod64.2.482] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Although earlier work has pointed to the presence of Na+/H+ exchangers (NHEs) in the rat epididymis, little is known about the regional distribution of various NHE isoforms and their functions. In the present work, expression of different isoforms of NHE in cultured epithelia of the efferent duct and cauda epdidymidis were studied. Reverse transcription-polymerase chain reaction revealed the presence of NHE1, NHE2, and NHE3, but not NHE4, message in both cultured epithelia. Western blot analysis detected the presence of NHE1 and NHE2 proteins in both cultured epithelia, but NHE3 protein was only detected in the cultured epithelial cells from the efferent duct. Immunohistochemical studies demonstrated that NHE2 was localized in the cytoplasm of the ciliated cells, whereas NHE3 was localized at the apical membrane of the principal cells of the efferent duct. The NHE activities in both cultured epithelia were inhibited by 10 microM HOE-694 (3-methylsulphonyl-4-piperidinobenzoyl guanidine methanesulphonate), a NHE1 inhibitor, by approximately 76%. The HOE-694-resistant NHE activities in the cultured epithelia of efferent duct and cauda epididymidis were completely inhibited by 20 microM S3226 (3-[2-(3-guanidino-2-methyl-3-oxo-propenyl)-5-methyl-phenyl]-N:-isopropylidene-2-methyl-acrylamide dihydrochloride), a NHE3 inhibitor, and 300 microM HOE-694 (a dose that can completely block NHE2), respectively. These results indicated that NHE1, NHE2, and NHE3 were expressed in the cultured epithelial cells of the efferent duct, whereas only NHE1 and NHE2 were expressed in the cultured epithelial cells of the cauda epididymidis. It is suggested that NHE1 may provide "housekeeping" functions in both epithelia, whereas NHE2 in the cauda epididymidis and NHE3 in the efferent duct may be involved in Na+ reabsorption and regulation of pH of the luminal fluid.
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Affiliation(s)
- G P Leung
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
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15
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Jacob P, Christiani S, Rossmann H, Lamprecht G, Vieillard-Baron D, Müller R, Gregor M, Seidler U. Role of Na(+)HCO(3)(-) cotransporter NBC1, Na(+)/H(+) exchanger NHE1, and carbonic anhydrase in rabbit duodenal bicarbonate secretion. Gastroenterology 2000; 119:406-19. [PMID: 10930376 DOI: 10.1053/gast.2000.9358] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS HCO(3)(-) supply to the enterocyte is rate limiting for duodenal HCO(3)(-) secretion (J(HCO3-)). This study defines the molecular nature of the major HCO(3)(-) uptake pathways in rabbit duodenocytes and investigates their physiologic significance and regulation during basal and stimulated J(HCO3-). METHODS & RESULTS pH gradient-driven (22)Na(+) uptake into duodenal basolateral membrane vesicles was partly HCO(3)(-) dependent, stilbene sensitive, and therefore mediated by Na(+)HCO(3)(-) cotransport, and partly HCO(3)(-) independent, Hoechst 642 sensitive, and therefore mediated by the Na(+)/H(+) exchanger isoform NHE1. Semiquantitative polymerase chain reaction (PCR) revealed high duodenal expression levels for the NBC1 isoform of the Na(+)HCO(3)(-) cotransporter gene family and NHE1. Cloning and comparison of full-length rabbit with human gastrointestinal and kidney NBC1 subtype revealed a conserved protein kinase A consensus sequence in the cytoplasmic N-terminus of the gastrointestinal NBC1. Inhibition of either Na(+)HCO(3)(-) cotransport or carbonic anhydrase reduced ouabain-sensitive J(HCO3-) in in vitro rabbit duodenal mucosae by approximately 50%, but did not affect 8-Br-cAMP-induced DeltaJ(HCO3-), suggesting cAMP-mediated up-regulation of the alternative pathway. However, inhibition of both Na(+)HCO(3)(-) cotransport and either carbonic anhydrase or NHE1 strongly reduced DeltaJ(HCO3-). CONCLUSIONS NBC1 and NHE1 are the major base importers in rabbit duodenocytes. Na(+)HCO(3)(-) cotransport and CO(2) hydration/Na(+)/H(+) exchange are equally important pathways for duodenal HCO(3)(-) supply and are up-regulated during cAMP-mediated stimulation.
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Affiliation(s)
- P Jacob
- Department I, Eberhard-Karls University, Tübingen, Germany
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16
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Shachaf C, Skorecki KL, Tzukerman M. Role of AP2 consensus sites in regulation of rat Npt2 (sodium-phosphate cotransporter) promoter. Am J Physiol Renal Physiol 2000; 278:F406-16. [PMID: 10710545 DOI: 10.1152/ajprenal.2000.278.3.f406] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Expression of the Npt2 gene, encoding the type II sodium-dependent phosphate cotransporter, is restricted to renal proximal tubule epithelium. We have isolated a 4,740-bp fragment of the 5'-flanking sequence of the rat Npt2 gene, identified the transcription initiation site, and demonstrated that this 5'-flanking sequence drives luciferase-reporter gene expression, following transfection in the proximal tubule cell-derived opossum kidney (OK) cell line but not in unrelated cell lines. Analysis of the promoter sequence revealed the presence of 10 consensus binding motifs for the AP2 transcription factor. Transient transfection assays revealed an important effect of the number of tandemly repeated AP2 sites in enhancing promoter activity. The promoter sequence also revealed a pair of inverted repeats enclosing 1,324 bp of intervening sequence and containing 8 of the total 10 AP2 consensus sites in the promoter sequence. Deletion or reversal of orientation of the distal inverted repeat resulted in marked enhancement of promoter activity. Electrophoretic mobility shift analysis revealed a distinct pattern of transcription factor binding to oligonucleotides containing AP2 sites, using nuclear extracts from OK cells, compared with unrelated cell lines. Taken together, these results suggest an important role for AP2 consensus binding sites in regulating Npt2 gene expression and suggest a mechanism of regulation mediated by the interaction of inverted repeats enclosing these sites.
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Affiliation(s)
- C Shachaf
- Bruce Rappaport Faculty of Medicine and Research Institute, Technion, Israel Institute of Technology, Department of Molecular Medicine, Rambam Medical Center, Haifa 31096, Israel
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Chew SB, Leung GP, Leung PY, Tse CM, Wong PY. Polarized distribution of NHE1 and NHE2 in the rat epididymis. Biol Reprod 2000; 62:755-8. [PMID: 10684820 DOI: 10.1095/biolreprod62.3.755] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Previous studies from our laboratory have provided evidence that the rat epididymis utilizes the Na(+)/H(+) exchanger to transport acid and base. The present study was undertaken to use immunohistochemistry for investigating the localization (apical versus basolateral) and distribution of NHE1 and NHE2 proteins along intact rat epididymis. Both proteins were found to be exclusively localized within the epithelium. Immunoreactivity for NHE1 was detected on the basolateral surface, whereas NHE2 immunoreactivity was detected on the apical side of the epithelium. Interestingly, NHE1 was found along the entire length of the epididymal tubule whereas NHE2 was absent in the initial segment but present in the caput, corpus, and cauda regions. These results, when interpreted along with those of previous functional studies, may suggest that the apical NHE2 is involved in Na(+) reabsorption and the basolateral NHE1 in HCO(3)(-) secretion in the rat epididymis.
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Affiliation(s)
- S B Chew
- Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
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Affiliation(s)
- L Counillon
- Laboratoire de Physiologie Cellulaire et Moléculaire, CNRS UMR 6548, 33 Av. de Valombrose, 06189 Nice, France
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Chapter 12 Molecular physiology of mammalian epithelial Na+/H+ exchangers NHE2 and NHE3. CURRENT TOPICS IN MEMBRANES 2000. [DOI: 10.1016/s1063-5823(00)50014-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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