scholarly journals Prolactin stimulates sodium and chloride ion channels in A6 renal epithelial cells

2015 ◽  
Vol 308 (7) ◽  
pp. F697-F705 ◽  
Author(s):  
Megan M. Greenlee ◽  
Jeremiah D. Mitzelfelt ◽  
Billie Jeanne Duke ◽  
Otor Al-Khalili ◽  
Hui-Fang Bao ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Chloride Transport ◽  
Anion Channel ◽  
Chloride Ion ◽  
Peptide Hormone ◽  
Open Probability ◽  
Renal Epithelial Cells ◽  
Electrophysiological Properties ◽  
A6 Cells ◽  
Pka Pathway

Many hormonal pathways contribute to the regulation of renal epithelial sodium channel (ENaC) function, a key process for maintaining blood volume and controlling blood pressure. In the present study, we examined whether the peptide hormone prolactin (PRL) regulates ENaC function in renal epithelial cells (A6). Basolateral application of several different concentrations of PRL dramatically stimulated the transepithelial current in A6 cells, increasing both amiloride-sensitive (ENaC) and amiloride-insensitive currents. Using cell-attached patch clamp, we determined that PRL increased both the number ( N) and open probability ( Po) of ENaC present in the apical membrane. Inhibition of PKA with H-89 abolished the effect of PRL on amiloride-sensitive and insensitive transepithelial currents and eliminated the increase in ENaC NPo with PRL exposure. PRL also increased cAMP in A6 cells, consistent with signaling through the cAMP-dependent PKA pathway. We also identified that PRL induced activity of a 2-pS anion channel with outward rectification, electrophysiological properties consistent with ClC4 or ClC5. RT-PCR only detected ClC4, but not ClC5 transcripts. Here, we show for the first time that PRL activates sodium and chloride transport in renal epithelial cells via ENaC and ClC4.

Purinergic control of apical plasma membrane PI(4,5)P2 levels sets ENaC activity in principal cells

2008 ◽  
Vol 294 (1) ◽  
pp. F38-F46 ◽  
Author(s):  
Oleh Pochynyuk ◽  
Vladislav Bugaj ◽  
Alain Vandewalle ◽  
James D. Stockand
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Purinergic Receptors ◽  
Apical Membrane ◽  
Purinergic Signaling ◽  
Apical Plasma Membrane ◽  
Resting Cells ◽  
Open Probability ◽  
Renal Epithelial Cells ◽  
Principal Cells

Activity of the epithelial sodium channel (ENaC) is limiting for Na+ reabsorption at the distal nephron. Phosphoinositides, such as phosphatidylinositol 4,5-biphosphate [PI(4,5)P2] modulate the activity of this channel. Activation of purinergic receptors triggers multiple events, including activation of PKC and PLC, with the latter depleting plasma membrane PI(4,5)P2. Here, we investigate regulation of ENaC in renal principal cells by purinergic receptors via PLC and PI(4,5)P2. Purinergic signaling rapidly decreases ENaC open probability and apical membrane PI(4,5)P2 levels with similar time courses. Moreover, inhibiting purinergic signaling with suramin rescues ENaC activity. The PLC inhibitor U73122, but not U73343, its inactive analog, recapitulates the action of suramin. In contrast, modulating PKC signaling failed to affect purinergic regulation of ENaC. Unexpectedly, inhibiting either purinergic receptors or PLC in resting cells dramatically increased ENaC activity above basal levels, indicating tonic activation of purinergic signaling in these polarized renal epithelial cells. Increased ENaC activity was associated with elevation of apical membrane PI(4,5)P2 levels. Subsequent treatment with ATP in the presence of inhibited purinergic signaling failed to decrease ENaC activity and apical membrane PI(4,5)P2 levels. Dwell-time analysis reveals that depletion of PI(4,5)P2 forces ENaC toward a closed state. In contrast, increasing PI(4,5)P2 levels above basal values locks the channel in an open state interrupted by brief closings. Thus our results suggest that purinergic control of apical membrane PI(4,5)P2 levels is a major regulator of ENaC activity in renal epithelial cells.

scholarly journals A synthetic prostone activates apical chloride channels in A6 epithelial cells

2008 ◽  
Vol 295 (2) ◽  
pp. G234-G251 ◽  
Author(s):  
Hui Fang Bao ◽  
Lian Liu ◽  
Julie Self ◽  
Billie Jeanne Duke ◽  
Ryuji Ueno ◽  
...  
Keyword(s):  
Chloride Channels ◽  
Driving Forces ◽  
Anion Channel ◽  
Hek293 Cells ◽  
Open Probability ◽  
Anion Secretion ◽  
A6 Cells ◽  
Low Concentrations ◽  
Voltage Dependent ◽  
Channel Type

The bicyclic fatty acid lubiprostone (formerly known as SPI-0211) activates two types of anion channels in A6 cells. Both channel types are rarely, if ever, observed in untreated cells. The first channel type was activated at low concentrations of lubiprostone (<100 nM) in >80% of cell-attached patches and had a unit conductance of ∼3–4 pS. The second channel type required higher concentrations (>100 nM) of lubiprostone to activate, was observed in ∼30% of patches, and had a unit conductance of 8–9 pS. The properties of the first type of channel were consistent with ClC-2 and the second with CFTR. ClC-2's unit current strongly inwardly rectified that could be best fit by models of the channel with multiple energy barrier and multiple anion binding sites in the conductance pore. The open probability and mean open time of ClC-2 was voltage dependent, decreasing dramatically as the patches were depolarized. The order of anion selectivity for ClC-2 was Cl > Br > NO3 > I > SCN, where SCN is thiocyanate. ClC-2 was a “double-barreled” channel favoring even numbers of levels over odd numbers as if the channel protein had two conductance pathways that opened independently of one another. The channel could be, at least, partially blocked by glibenclamide. The properties of the channel in A6 cells were indistinguishable from ClC-2 channels stably transfected in HEK293 cells. CFTR in the patches had a selectivity of Cl > Br ≫ NO3 ≅ SCN ≅ I. It outwardly rectified as expected for a single-site anion channel. Because of its properties, ClC-2 is uniquely suitable to promote anion secretion with little anion reabsorption. CFTR, on the other hand, could promote either reabsorption or secretion depending on the anion driving forces.

Hormonal Regulation of Sodium/Sulfate Co-Transport in Renal Epithelial Cells

2000 ◽  
Vol 225 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Hwa Jeong Lee ◽  
Kazuko Sagawa ◽  
Wei Shi ◽  
Heini Murer ◽  
Marilyn E. Morris
Keyword(s):  
Epithelial Cells ◽  
Sodium Sulfate ◽  
Hormonal Regulation ◽  
Renal Epithelial Cells

scholarly journals Super-resolution microscopy reveals that Na+/K+-ATPase signaling protects against glucose-induced apoptosis by deactivating Bad

2021 ◽  
Vol 12 (8) ◽  
Author(s):  
Kristoffer Bernhem ◽  
Jacopo M. Fontana ◽  
Daniel Svensson ◽  
Liang Zhang ◽  
Linnéa M. Nilsson ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Chronic Diseases ◽  
Kidney Diseases ◽  
Super Resolution ◽  
Diabetic Patients ◽  
Diabetic Kidney ◽  
Renal Epithelial Cells ◽  
Apoptotic Process ◽  
Induced Apoptosis ◽  
Super Resolution Microscopy

AbstractActivation of the apoptotic pathway is a major cause of progressive loss of function in chronic diseases such as neurodegenerative and diabetic kidney diseases. There is an unmet need for an anti-apoptotic drug that acts in the early stage of the apoptotic process. The multifunctional protein Na+,K+-ATPase has, in addition to its role as a transporter, a signaling function that is activated by its ligand, the cardiotonic steroid ouabain. Several lines of evidence suggest that sub-saturating concentrations of ouabain protect against apoptosis of renal epithelial cells, a common complication and major cause of death in diabetic patients. Here, we induced apoptosis in primary rat renal epithelial cells by exposing them to an elevated glucose concentration (20 mM) and visualized the early steps in the apoptotic process using super-resolution microscopy. Treatment with 10 nM ouabain interfered with the onset of the apoptotic process by inhibiting the activation of the BH3-only protein Bad and its translocation to mitochondria. This occurred before the pro-apoptotic protein Bax had been recruited to mitochondria. Two ouabain regulated and Akt activating Ca2+/calmodulin-dependent kinases were found to play an essential role in the ouabain anti-apoptotic effect. Our results set the stage for further exploration of ouabain as an anti-apoptotic drug in diabetic kidney disease as well as in other chronic diseases associated with excessive apoptosis.

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