scholarly journals The Drosophila NKCC Ncc69 is required for normal renal tubule function

2012 ◽  
Vol 303 (8) ◽  
pp. C883-C894 ◽  
Author(s):  
Aylin R. Rodan ◽  
Michel Baum ◽  
Chou-Long Huang
Keyword(s):  
Ion Transport ◽  
Renal Tubule ◽  
Basolateral Membrane ◽  
Malpighian Tubule ◽  
Transport Processes ◽  
Wild Type ◽  
Atpase Inhibitor ◽  
Transport Pathways ◽  
Epithelial Ion Transport

Epithelial ion transport is essential to renal homeostatic function, and it is dysregulated in several diseases, such as hypertension. An understanding of the insect renal (Malpighian) tubule yields insights into conserved epithelial ion transport processes in higher organisms and also has implications for the control of insect infectious disease vectors. Here, we examine the role of the Na+-K+-2Cl− (NKCC) cotransporter Ncc69 in Drosophila tubule function. Ncc69 mutant tubules have decreased rates of fluid secretion and K+ flux, and these phenotypes were rescued by expression of wild-type Ncc69 in the principal cells of the tubule. Na+ flux was unaltered in Ncc69 mutants, suggesting Na+ recycling across the basolateral membrane. In unstimulated tubules, the principal role of the Na+-K+-ATPase is to generate a favorable electrochemical gradient for Ncc69 activity: while the Na+-K+-ATPase inhibitor ouabain decreased K+ flux in wild-type tubules, it had no effect in Ncc69 mutant tubules. However, in the presence of cAMP, which stimulates diuresis, additional Na+-K+-ATPase-dependent K+ transport pathways are recruited. In studying the effects of capa-1 on wild-type and Ncc69 mutant tubules, we found a novel antidiuretic role for this hormone that is dependent on intact Ncc69, as it was abolished in Ncc69 mutant tubules. Thus, Ncc69 plays an important role in transepithelial ion and fluid transport in the fly renal tubule and is a target for regulation in antidiuretic states.

scholarly journals Ion Transport by Pulmonary Epithelia

2011 ◽  
Vol 2011 ◽  
pp. 1-16 ◽  
Author(s):  
Monika I. Hollenhorst ◽  
Katrin Richter ◽  
Martin Fronius
Keyword(s):  
Ion Transport ◽  
Fluid Layer ◽  
Alveolar Epithelium ◽  
Cell Types ◽  
Transport Processes ◽  
Alveolar Type ◽  
Type I ◽  
Basal Cells ◽  
Epithelial Ion Transport

The lung surface of air-breathing vertebrates is formed by a continuous epithelium that is covered by a fluid layer. In the airways, this epithelium is largely pseudostratified consisting of diverse cell types such as ciliated cells, goblet cells, and undifferentiated basal cells, whereas the alveolar epithelium consists of alveolar type I and alveolar type II cells. Regulation and maintenance of the volume and viscosity of the fluid layer covering the epithelium is one of the most important functions of the epithelial barrier that forms the outer surface area of the lungs. Therefore, the epithelial cells are equipped with a wide variety of ion transport proteins, among which Na+, Cl−, and K+channels have been identified to play a role in the regulation of the fluid layer. Malfunctions of pulmonary epithelial ion transport processes and, thus, impairment of the liquid balance in our lungs is associated with severe diseases, such as cystic fibrosis and pulmonary oedema. Due to the important role of pulmonary epithelial ion transport processes for proper lung function, the present paper summarizes the recent findings about composition, function, and ion transport properties of the airway epithelium as well as of the alveolar epithelium.

Voltage clamping single cells in intact Malpighian tubules of mosquitoes

2000 ◽  
Vol 279 (4) ◽  
pp. F747-F754 ◽  
Author(s):  
R. Masia ◽  
D. Aneshansley ◽  
W. Nagel ◽  
R. J. Nachman ◽  
K. W. Beyenbach
Keyword(s):  
Apical Membrane ◽  
Single Cells ◽  
Basolateral Membrane ◽  
Malpighian Tubule ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Malpighian Tubules ◽  
Shunt Resistance ◽  
Transport Pathways ◽  
Principal Cells

Principal cells of the Malpighian tubule of the yellow fever mosquito were studied with the methods of two-electrode voltage clamp (TEVC). Intracellular voltage ( V pc) was −86.7 mV, and input resistance ( R pc) was 388.5 kΩ ( n = 49 cells). In six cells, Ba2+ (15 mM) had negligible effects on V pc, but it increased R pc from 325.3 to 684.5 kΩ ( P< 0.001). In the presence of Ba2+, leucokinin-VIII (1 μM) increased V pc to −101.8 mV ( P < 0.001) and reduced R pc to 340.2 kΩ ( P < 0.002). Circuit analysis yields the following: basolateral membrane resistance, 652.0 kΩ; apical membrane resistance, 340.2 kΩ; shunt resistance ( R sh), 344.3 kΩ; transcellular resistance, 992.2 kΩ. The fractional resistance of the apical membrane (0.35) and the ratio of transcellular resistance and R sh (3.53) agree closely with values obtained by cable analysis in isolated perfused tubules and confirm the usefulness of TEVC methods in single principal cells of the intact Malpighian tubule. Dinitrophenol (0.1 mM) reversibly depolarized V pc from −94.3 to −10.7 mV ( P< 0.001) and reversibly increased R pc from 412 to 2,879 kΩ ( P < 0.001), effects that were duplicated by cyanide (0.3 mM). Significant effects of metabolic inhibition on voltage and resistance suggest a role of ATP in electrogenesis and the maintenance of conductive transport pathways.

scholarly journals KCNJ10 (Kir4.1) is expressed in the basolateral membrane of the cortical thick ascending limb

2015 ◽  
Vol 308 (11) ◽  
pp. F1288-F1296 ◽  
Author(s):  
Chengbiao Zhang ◽  
Lijun Wang ◽  
Xiao-Tong Su ◽  
Dao-Hong Lin ◽  
Wen-Hui Wang
Keyword(s):  
Basolateral Membrane ◽  
Reversal Potential ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Initial Part ◽  
Wild Type ◽  
Open Probability ◽  
Cell Recording ◽  
Late Part

The aim of the present study is to examine the role of Kcnj10 (Kir.4.1) in contributing to the basolateral K conductance in the cortical thick ascending limb (cTAL) using Kcnj10+/+ wild-type (WT) and Kcnj10−/− knockout (KO) mice. The patch-clamp experiments detected a 40- and an 80-pS K channel in the basolateral membrane of the cTAL. Moreover, the probability of finding the 40-pS K was significantly higher in the late part of the cTAL close to the distal convoluted tubule than those in the initial part. Immunostaining showed that Kcnj10 staining was detected in the basolateral membrane of the cTAL but the expression was not uniformly distributed. The disruption of Kcnj10 completely eliminated the 40-pS K channel but not the 80-pS K channel, suggesting the role of Kcnj10 in forming the 40-pS K channel of the cTAL. Also, the disruption of Kcnj10 increased the probability of finding the 80-pS K channel in the cTAL, especially in the late part of the cTAL. Because the channel open probability of the 80-pS K channel in KO was similar to those of WT mice, the increase in the 80-pS K channel may be achieved by increasing K channel number. The whole cell recording further showed that K reversal potential measured with 5 mM K in the bath and 140 mM K in the pipette was the same in the WT and KO mice. Moreover, Western blot and immunostaining showed that the disruption of Kcnj10 did not affect the expression of Na-K-Cl cotransporter 2 (NKCC2). We conclude that Kir.4.1 is expressed in the basolateral membrane of cTAL and that the disruption of Kir.4.1 has no significant effect on the membrane potential of the cTAL and NKCC2 expression.

scholarly journals Rab8 promotes polarized membrane transport through reorganization of actin and microtubules in fibroblasts.

1996 ◽  
Vol 135 (1) ◽  
pp. 153-167 ◽  
Author(s):  
J Peränen ◽  
P Auvinen ◽  
H Virta ◽  
R Wepf ◽  
K Simons
Keyword(s):  
Epithelial Cells ◽  
Membrane Transport ◽  
Vesicular Stomatitis Virus ◽  
Actin Filaments ◽  
Mdck Cells ◽  
Basolateral Membrane ◽  
Wild Type ◽  
Expression Systems ◽  
Vesicular Stomatitis

Rab8 is a small Ras-like GTPase that regulates polarized membrane transport to the basolateral membrane in epithelial cells and to the dendrites in neurons. It has recently been demonstrated that fibroblasts sort newly synthesized proteins into two different pathways for delivery to the cell surface that are equivalent to the apical and the basolateral post-Golgi routes in epithelial cells (Yoshimori, T., P. Keller, M.G. Roth, and K. Simons. 1996. J. Cell Biol. 133:247-256). To determine the role of Rab8 in fibroblasts, we used both transient expression systems and stable cell lines expressing mutant or wild-type (wt) Rab8. A dramatic change in cell morphology occurred in BHK cells expressing both the wt Rab8 and the activated form of the GTPase, the Rab8Q67L mutant. These cells formed processes as a result of a reorganization of both their actin filaments and microtubules. Newly synthesized vesicular stomatitis virus G glycoprotein, a basolateral marker protein in MDCK cells, was preferentially delivered into these cell outgrowths. Based on these findings, we propose that Rab8 provides a link between the machinery responsible for the formation of cell protrusions and polarized biosynthetic membrane traffic.

PAT-1 (Slc26a6) is the predominant apical membrane Cl−/HCO3− exchanger in the upper villous epithelium of the murine duodenum

2007 ◽  
Vol 292 (4) ◽  
pp. G1079-G1088 ◽  
Author(s):  
Janet E. Simpson ◽  
Clifford W. Schweinfest ◽  
Gary E. Shull ◽  
Lara R. Gawenis ◽  
Nancy M. Walker ◽  
...  
Keyword(s):  
Anion Exchanger ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Duodenal Mucosa ◽  
Transport Processes ◽  
Wild Type ◽  
Rt Pcr ◽  
Targeted Deletion ◽  
Anion Transporter ◽  
Dependent Transport

Basal HCO3− secretion across the duodenum has been shown in several species to principally involve the activity of apical membrane Cl−/HCO3− exchanger(s). To investigate the identity of relevant anion exchanger(s), experiments were performed using wild-type (WT) mice and mice with gene-targeted deletion of the following Cl−/HCO3− exchangers localized to the apical membrane of murine duodenal villi: Slc26a3 [down-regulated in adenoma (DRA)], Slc26a6 [putative anion transporter 1 (PAT-1)], and Slc4a9 [anion exchanger 4 (AE4)]. RT-PCR of the isolated villous epithelium demonstrated PAT-1, DRA, and AE4 mRNA expression. Using the pH-sensitive dye BCECF, anion exchange rates were measured across the apical membrane of epithelial cells in the upper villus of the intact duodenal mucosa. Under basal conditions, Cl−/HCO3− exchange activity was reduced by 65–80% in the PAT-1(−) duodenum, 30–40% in the DRA(−) duodenum, and <5% in the AE4(−) duodenum compared with the WT duodenum. SO42−/HCO3− exchange was eliminated in the PAT-1(−) duodenum but was not affected in the DRA(−) and AE4(−) duodenum relative to the WT duodenum. Intracellular pH (pHi) was reduced in the PAT-1(−) villous epithelium but increased to WT levels in the absence of CO2/HCO3− or during methazolamide treatment. Further experiments under physiological conditions indicated active pHi compensation in the PAT-1(−) villous epithelium by combined activities of Na+/H+ exchanger 1 and Cl−-dependent transport processes at the basolateral membrane. We conclude that 1) PAT-1 is the major contributor to basal Cl−/HCO3− and SO42−/HCO3− exchange across the apical membrane and 2) PAT-1 plays a role in pHi regulation in the upper villous epithelium of the murine duodenum.

Expression of claudin-7 and -8 along the mouse nephron

2004 ◽  
Vol 286 (6) ◽  
pp. F1063-F1071 ◽  
Author(s):  
Wing Y. Li ◽  
Catherine L. Huey ◽  
Alan S. L. Yu
Keyword(s):  
Tight Junction ◽  
Renal Tubule ◽  
Basolateral Membrane ◽  
Paracellular Permeability ◽  
Mouse Kidney ◽  
Integral Membrane Proteins ◽  
Distal Nephron ◽  
Nephron Segments ◽  
Nephron Segment

Claudins are integral membrane proteins of the tight junction that determine the magnitude and selectivity of paracellular permeability in epithelial tissues. The mammalian renal tubule exhibits considerable heterogeneity in the permeability properties of its different segments. To determine the nephron segment localization of claudin-7 and -8, immunofluorescence staining of mouse kidney sections was performed using isoform-specific antibodies. Claudin-8 was found to be expressed primarily at the tight junction along the entire aldosterone-sensitive distal nephron and in the late segments of the thin descending limbs of long-looped nephrons. This pattern of expression is consistent with the putative role of claudin-8 as a paracellular cation barrier. By contrast, claudin-7 was found in the same nephron segments as claudin-8, but it was expressed primarily at the basolateral membrane.

Turtle urinary bladder: regulation of ion transport by dynamic changes in plasma membrane area

1989 ◽  
Vol 257 (5) ◽  
pp. R973-R981
Author(s):  
D. L. Stetson
Keyword(s):  
Urinary Bladder ◽  
Ion Transport ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Transport Processes ◽  
Granular Cells ◽  
Membrane Area ◽  
Low Co2 ◽  
In Series ◽  
Cl Channels

Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and HCO3- secretion-Cl- absorption. Each transport process is performed by a specific epithelial cell type. Granular cells absorb Na+ but they are not sensitive to antidiuretic hormone (ADH), unlike toad bladder granular cells. alpha-Carbonic anhydrase-rich (CA) cells secrete H+ via an apical H+-adenosinetriphosphatase (ATPase). Under conditions of low CO2 tension, this active pump is contained in the limiting membranes of certain cytoplasmic vesicles. The vesicles fuse with the apical membrane, and H+ pumps are incorporated into that membrane, as physiological conditions demand increased H+ secretion. The stimulus for fusion of these vesicles with the apical membrane appears to be intracellular acidification. beta-CA cells secrete HCO3- and reabsorb Cl-, both processes driven by H+-ATPase in the basolateral membrane in series with an apical Cl- -HCO3- exchanger. Increased intracellular adenosine 3',5'-cyclic monophosphate concentration in beta-cells stimulates net HCO3- secretion and induces an electrogenic component of this flux by activating an apical Cl- channel. This activation accompanies the fusion of an intracellular tubulovesicular network with the apical membrane. The membrane of this network may contain Cl- channels.

Transepithelial HCO3− absorption is defective in renal thick ascending limbs from Na+/H+ exchanger NHE1 null mutant mice

2004 ◽  
Vol 287 (6) ◽  
pp. F1244-F1249 ◽  
Author(s):  
David W. Good ◽  
Bruns A. Watts ◽  
Thampi George ◽  
Jamie W. Meyer ◽  
Gary E. Shull
Keyword(s):  
Rat Kidney ◽  
Basolateral Membrane ◽  
Thick Ascending Limb ◽  
Wild Type ◽  
Medullary Thick Ascending Limb ◽  
Transepithelial Voltage ◽  
Regulatory Defect ◽  
Null Mutant Mice

In the medullary thick ascending limb (MTAL) of rat kidney, inhibiting basolateral Na+/H+ exchange with either amiloride or nerve growth factor (NGF) results secondarily in inhibition of apical Na+/H+ exchange, thereby decreasing transepithelial HCO3− absorption. To assess the possible role of the Na+/H+ exchanger NHE1 in this regulatory process, MTALs from wild-type and NHE1 knockout (NHE1−/−) mice were studied using in vitro microperfusion. The rate of HCO3− absorption was decreased 60% in NHE1−/− MTALs (15.4 ± 0.5 pmol·min−1·mm−1 wild-type vs. 6.0 ± 0.5 pmol·min−1·mm−1 NHE1−/−). Transepithelial voltage, an index of the NaCl absorption rate, did not differ in wild-type and NHE1−/− MTALs. Basolateral addition of 10 μM amiloride or 0.7 nM NGF decreased HCO3− absorption by 45–49% in wild-type MTALs but had no effect on HCO3− absorption in NHE1−/− MTALs. Inhibition of HCO3− absorption by vasopressin and stimulation by hyposmolality, both of which regulate MTAL HCO3− absorption through primary effects on apical Na+/H+ exchange, were similar in wild-type and NHE1−/− MTALs. Thus the regulatory defect in NHE1−/− MTALs is specific for factors (bath amiloride and NGF) shown previously to inhibit HCO3− absorption through primary effects on basolateral Na+/H+ exchange. These findings demonstrate a novel role for NHE1 in transepithelial HCO3− absorption in the MTAL, in which basolateral NHE1 controls the activity of apical NHE3. Paradoxically, a reduction in NHE1-mediated H+ extrusion across the basolateral membrane leads to a decrease in apical Na+/H+ exchange activity that reduces HCO3− absorption.

scholarly journals The role of bestrophin in airway epithelial ion transport

FEBS Letters ◽  
2004 ◽  
Vol 577 (3) ◽  
pp. 551-554 ◽  
Author(s):  
Valentin Duta ◽  
Artur J. Szkotak ◽  
Drew Nahirney ◽  
Marek Duszyk
Keyword(s):  
Ion Transport ◽  
Airway Epithelial ◽  
Epithelial Ion Transport
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