Cloning and localization of a double-pore K channel, KCNK1: exclusive expression in distal nephron segments

1997 ◽  
Vol 273 (4) ◽  
pp. F663-F666 ◽  
Author(s):  
Marcelo Orias ◽  
Heino Velázquez ◽  
Freeman Tung ◽  
George Lee ◽  
Gary V. Desir
Keyword(s):  
Amino Acid ◽  
Collecting Duct ◽  
Human Kidney ◽  
Distal Tubule ◽  
Amino Acid Identity ◽  
Northern Analysis ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
K Channels

The K-selective channel, TOK1, recently identified in yeast, displays the unusual structural feature of having two putative pore regions, in contrast to all previously cloned K channels. Using the TOK1 pore regions as probes, we identified a human kidney cDNA encoding a 337-amino acid protein (hKCNK1) with four transmembrane segments and two pore regions containing the signature sequence of K channels. Amino acid identity to TOK1 is only 15% overall but 40% at the pores. Northern analysis indicates high expression of a 1.9-kb message in brain > kidney >> heart. Nephron segment localization, carried out in rabbit by reverse transcription-polymerase chain reaction, reveals that KCNK1 is expressed in cortical thick ascending limb, connecting tubule, and cortical collecting duct. It was not detected in the proximal tubule, medullary thick ascending limb, distal convoluted tubule, and glomerulus. We conclude that KCNK1 is a unique, double-pore, mammalian K channel, distantly related to the yeast channel TOK1, that is expressed in distal tubule and is a candidate to participate in renal K homeostasis.

Arachidonic acid inhibits activity of cloned renal K+ channel, ROMK1

1996 ◽  
Vol 271 (3) ◽  
pp. F588-F594 ◽  
Author(s):  
C. M. Macica ◽  
Y. Yang ◽  
S. C. Hebert ◽  
W. H. Wang
Keyword(s):  
Arachidonic Acid ◽  
Membrane Fluidity ◽  
Collecting Duct ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Channel Activity ◽  
Lipoxygenase Inhibitor ◽  
Open Probability ◽  
Apical Membranes

Arachidonic acid (AA) has been shown to inhibit the activity of the low-conductance ATP-sensitive K+ channel in the apical membrane of the cortical collecting duct [W. Wang, A. Cassola, and G. Giebisch. Am. J. Physiol. 262 (Renal Fluid Electrolyte Physiol. 31): F554-F559, 1992]. ROMK1, a K+ channel derived from the rat renal outer medulla, shares many biophysical properties of the native low-conductance K+ channel, which is localized to the apical membranes of the cortical collecting duct and thick ascending limb. This study was designed to determine whether the ROMK channel maintains the property of AA sensitivity of the native low-conductance K+ channel. Experiments were conducted in Xenopus oocytes injected with cRNA encoding the ROMK1 channel by use of patch-clamp techniques. We have confirmed previous reports that the cloned ROMK1 has similar channel kinetics, high open probability, and inward slope conductance as the native low-conductance K+ channel, respectively. Addition of 5 microM AA to an inside-out patch resulted in reversible inhibition of channel activity at a concentration similar to the inhibitor constant for AA on the native K+ channel. The effect of AA on channel activity was preserved in the presence of 10 microM indomethacin, a cyclooxygenase inhibitor, 4 microM cinnamyl-3,4-dihydroxycyanocinnamate, a lipoxygenase inhibitor, and 4 microM 17-octadecynoic acid, an inhibitor of cytochrome P-450 monooxygenases, thus indicating that the effect of AA was not mediated by metabolites of AA. The effect did not appear to be the result of changes in membrane fluidity, since 5 microM eicosatetraynoic acid, an AA analogue that is a potent modulator of membrane fluidity, had no effect. Furthermore, the addition of AA to the outside of the patch also had no effect on channel activity. These results indicate that, like the native low-conductance channel, AA is able to directly inhibit ROMK1 channel activity.

scholarly journals Arachidonic acid inhibits basolateral K channels in the cortical collecting duct via cytochrome P-450 epoxygenase-dependent metabolic pathways

2008 ◽  
Vol 294 (6) ◽  
pp. F1441-F1447 ◽  
Author(s):  
ZhiJian Wang ◽  
Yuan Wei ◽  
John R. Falck ◽  
Krishnam Raju Atcha ◽  
Wen-Hui Wang
Keyword(s):  
Arachidonic Acid ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Inhibitory Effect ◽  
K Channel ◽  
Dependent Manner ◽  
Cortical Collecting Duct ◽  
Patch Clamp Technique ◽  
K Channels ◽  
Cytochrome P 450

We used the patch-clamp technique to study the effect of arachidonic acid (AA) on basolateral 18-pS K channels in the principal cell of the cortical collecting duct (CCD) of the rat kidney. Application of AA inhibited the 18-pS K channels in a dose-dependent manner and 10 μM AA caused a maximal inhibition. The effect of AA on the 18-pS K channel was specific because application of 11,14,17-eicosatrienoic acid had no effect on channel activity. Also, the inhibitory effect of AA on the 18-pS K channels was abolished by blocking cytochrome P-450 (CYP) epoxygenase with N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide (MS-PPOH) but was not affected by inhibiting CYP ω-hydroxylase or cyclooxygenase. The notion that the inhibitory effect of AA was mediated by CYP epoxygenase-dependent metabolites was further supported by the observation that application of 100 nM 11,12-epoxyeicosatrienoic acid (EET) mimicked the effect of AA and inhibited the basolateral 18-pS K channels. In contrast, addition of either 5,6-, 8,9-, or 14,15-EET failed to inhibit the 18-pS K channels. Moreover, application of 11,12-EET was still able to inhibit the 18-pS K channels in the presence of MS-PPOH. This suggests that 11,12-EET is a mediator for the AA-induced inhibition of the 18-pS K channels. We conclude that AA inhibits basolateral 18-pS K channels by a CYP epoxygenase-dependent pathway and that 11,12-EET is a mediator for the effect of AA on basolateral K channels in the CCD.

Dietary K+ regulates apical membrane expression of maxi-K channels in rabbit cortical collecting duct

2005 ◽  
Vol 289 (4) ◽  
pp. F922-F932 ◽  
Author(s):  
Fadi Najjar ◽  
Hao Zhou ◽  
Tetsuji Morimoto ◽  
James B. Bruns ◽  
Hai-Sheng Li ◽  
...  
Keyword(s):  
Apical Membrane ◽  
Collecting Duct ◽  
K Channel ◽  
Ambystoma Tigrinum ◽  
Intercalated Cells ◽  
Sk Channels ◽  
Cortical Collecting Duct ◽  
Α Subunit ◽  
K Channels ◽  
Channel Density

The cortical collecting duct (CCD) is a final site for regulation of K+ homeostasis. CCD K+ secretion is determined by the electrochemical gradient and apical permeability to K+. Conducting secretory K+ (SK/ROMK) and maxi-K channels are present in the apical membrane of the CCD, the former in principal cells and the latter in both principal and intercalated cells. Whereas SK channels mediate baseline K+ secretion, maxi-K channels appear to participate in flow-stimulated K+ secretion. Chronic dietary K+ loading enhances the CCD K+ secretory capacity due, in part, to an increase in SK channel density (Palmer et al., J Gen Physiol 104: 693–710, 1994). Long-term exposure of Ambystoma tigrinum to elevated K+ increases renal K+ excretion due to an increase in apical maxi-K channel density in their CDs (Stoner and Viggiano, J Membr Biol 162: 107–116, 1998). The purpose of the present study was to test whether K+ adaptation in the mammalian CCD is associated with upregulation of maxi-K channel expression. New Zealand White rabbits were fed a low (LK), control (CK), or high (HK) K+ diet for 10–14 days. Real-time PCR quantitation of message encoding maxi-K α- and β2–4-subunits in single CCDs from HK animals was greater than that detected in CK and LK animals ( P < 0.05); β1-subunit was not detected in any CCD sample but was present in whole kidney. Indirect immunofluorescence microscopy revealed a predominantly intracellular distribution of α-subunits in LK kidneys. In contrast, robust apical labeling was detected primarily in α-intercalated cells in HK kidneys. In summary, K+ adaptation is associated with an increase in steady-state abundance of maxi-K channel subunit-specific mRNAs and immunodetectable apical α-subunit, the latter observation consistent with redistribution from an intracellular pool to the plasma membrane.

The Protein Tyrosine Kinase-Dependent Pathway Mediates the Effect of K Intake on Renal K Secretion

Physiology ◽  
2005 ◽  
Vol 20 (2) ◽  
pp. 140-146 ◽  
Author(s):  
Dao-Hong Lin ◽  
Hyacinth Sterling ◽  
Wen-Hui Wang
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Protein Tyrosine Kinase ◽  
Collecting Duct ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Cortical Collecting Duct ◽  
Protein Tyrosine ◽  
K Secretion ◽  
Dependent Pathway

Dietary K intake plays an important role in the regulation of K secretion: a decrease stimulates and an increase suppresses kidney expression of protein tyrosine kinase (PTK), which plays a role in regulating Kir1.1 (ROMK), which is responsible for K secretion in the cortical collecting duct (CCD) and K recycling in the thick ascending limb. Tyrosine phosphorylation of ROMK channels increases with low dietary K and decreases with high dietary K. Moreover, stimulation of tyrosine phosphorylation of ROMK1 enhances ROMK1 internalization and reduces the K channel number in the cell surface in the CCD.

Segmental expression of somatostatin receptor subtypes sst1 and sst2 in tubules and glomeruli of human kidney

2001 ◽  
Vol 280 (3) ◽  
pp. F457-F465 ◽  
Author(s):  
Douglas A. Balster ◽  
M. Sue O'Dorisio ◽  
Monica A. Summers ◽  
Martin A. Turman
Keyword(s):  
Cell Function ◽  
Collecting Duct ◽  
Somatostatin Receptor ◽  
Human Kidney ◽  
Distal Tubule ◽  
Receptor Subtypes ◽  
Thick Ascending Limb ◽  
Somatostatin Receptor Subtypes ◽  
Normal Human Kidney ◽  
Normal Human

Somatostatin is known to modulate mesangial and tubular cell function and growth, but the somatostatin receptor (sst) subtypes responsible for these effects have not been defined. There are at least five different sst receptor subtypes (sst1-sst5). We used RT-PCR to demonstrate that normal human kidney consistently expresses mRNA for sst1 and sst2 (9 of 9 donors). Some donors expressed sst4 or sst5mRNA, but none expressed sst3 mRNA. Expression of sst1 and sst2 was further assessed by staining serial sections of normal human kidney with sst1 and sst2 antisera, Arachis hypogaea (AH) lectin (to define distal tubule/collecting duct cells), Phaseolus vulgaris lectin (proximal tubules), and Tamm-Horsfall protein (THP) antiserum (thick ascending limb of the loop of Henle). Specificity of antisera was demonstrated by transfection and absorption studies. Sst2, but not sst1, was expressed in glomeruli. Intense sst1 and sst2 staining localized exclusively to AH+ and THP+ tubules. Thus sst1 and sst2 subtype-selective analogs may be useful to beneficially modulate renal cell function in pathological conditions.

scholarly journals Renal cortical regulation of COX-1 and functionally related products in early renovascular hypertension (rat)

2006 ◽  
Vol 291 (5) ◽  
pp. F987-F994 ◽  
Author(s):  
F. Theilig ◽  
H. Debiec ◽  
B. Nafz ◽  
P. Ronco ◽  
R. Nüsing ◽  
...  
Keyword(s):  
Renovascular Hypertension ◽  
Collecting Duct ◽  
Distal Tubule ◽  
Prostaglandin E ◽  
Thick Ascending Limb ◽  
Receptor Blockade ◽  
Ang Ii ◽  
Cortical Collecting Duct ◽  
Cox 2 ◽  
Cox 1

Renal volume regulation is modulated by the action of cyclooxygenases (COX) and the resulting generation of prostanoids. Epithelial expression of COX isoforms in the cortex directs COX-1 to the distal convolutions and cortical collecting duct, and COX-2 to the thick ascending limb. Partly colocalized are prostaglandin E synthase (PGES), the downstream enzyme for renal prostaglandin E2 (PGE2) generation, and the EP receptors type 1 and 3. COX-1 and related components were studied in two kidney-one clip (2K1C) Goldblatt hypertensive rats with combined chronic ANG II or bradykinin B2 receptor blockade using candesartan (cand) or the B2 antagonist Hoechst 140 (Hoe). Rats (untreated sham, 2K1C, sham + cand, 2K1C + cand, sham + Hoe, 2K1C + Hoe) were treated to map expression of parameters controlling PGE2 synthesis. In 2K1C, cortical COX isoforms did not change uniformly. COX-2 changed in parallel with NO synthase 1 (NOS1) expression with a raise in the clipped, but a decrease in the nonclipped side. By contrast, COX-1 and PGES were uniformly downregulated in both kidneys, along with reduced urinary PGE2 levels, and showed no clear relations with the NO status. ANG II receptor blockade confirmed negative regulation of COX-2 by ANG II but blunted the decrease in COX-1 selectively in nonclipped kidneys. B2 receptor blockade reduced COX-2 induction in 2K1C but had no clear effect on COX-1. We suggest that in 2K1C, COX-1 and PGES expression may fail to oppose the effects of renovascular hypertension through reduced prostaglandin signaling in late distal tubule and cortical collecting duct.

Expression of the thiazide-sensitive Na-Cl cotransporter in rat and human kidney

1995 ◽  
Vol 269 (6) ◽  
pp. F900-F910 ◽  
Author(s):  
N. Obermuller ◽  
P. Bernstein ◽  
H. Velazquez ◽  
R. Reilly ◽  
D. Moser ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Human Kidney ◽  
Protein Band ◽  
Distal Region ◽  
Thick Ascending Limb ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Nephron Segments ◽  
Collecting Tubule

An electroneutral thiazide-sensitive Na-Cl cotransport pathway (TSC) has been localized functionally to the distal convoluted tubule (DCT), although the TSC has also been detected in the connecting tubule (CNT), the cortical collecting duct, and the medullary collecting tubule as well. The present experiments were designed to localize expression of message for the TSC in rat and human kidney. A riboprobe, generated from the mouse TSC, was used for in situ hybridization. Simultaneous immunocytochemistry, using antibodies to Tamm-Horsfall protein, band 3, and the Na+/Ca2+ exchanger, permitted delineation of specific nephron segments. In rat, message for the TSC was highly expressed in DCT cells but not elsewhere. The transition from thick ascending limb to DCT was abrupt, whereas the transition to CNT was gradual. In the more distal region of rat DCT (DCT-2), which contained few intercalated cells, both TSC message and Na+/Ca2+ exchanger immunoreactivity were present. Treatment of rats with furosemide for 5 days increased expression of TSC message within the DCT but did not induce its expression elsewhere. In humans, expression of TSC message was also highest in cells of the DCT. In humans, however, expression extended well into the CNT. These experiments indicate that the TSC is expressed predominantly by DCT cells in both rat and humans, although expression extends into the CNT cells in humans. They also show that the TSC and Na+/Ca2+ exchanger are coexpressed by a subpopulation of DCT cells near the junction with the CNT.

Ontogeny of flow-stimulated potassium secretion in rabbit cortical collecting duct: functional and molecular aspects

2003 ◽  
Vol 285 (4) ◽  
pp. F629-F639 ◽  
Author(s):  
Craig B. Woda ◽  
Nobuyuki Miyawaki ◽  
Santhanam Ramalakshmi ◽  
Mohan Ramkumar ◽  
Raul Rojas ◽  
...  
Keyword(s):  
Collecting Duct ◽  
Cell Labeling ◽  
K Channel ◽  
Urinary Flow ◽  
Intercalated Cells ◽  
Cortical Collecting Duct ◽  
Α Subunit ◽  
K Channels ◽  
K Secretion ◽  
High Conductance

High urinary flow rates stimulate K secretion in the fully differentiated but not neonatal or weanling rabbit cortical collecting duct (CCD). Both small-conductance secretory K and high-conductance Ca2+/stretch-activated maxi-K channels have been identified in the apical membrane of the mature CCD by patch-clamp analysis. We reported that flow-stimulated net K secretion in the adult rabbit CCD is 1) blocked by TEA and charybdotoxin, inhibitors of intermediate- and high-conductance (maxi-K) Ca2+-activated K channels, and 2) associated with increases in net Na absorption and intracellular Ca2+ concentration ([Ca2+]i). The present study examined whether the absence of flow-stimulated K secretion early in life is due to a 1) limited flow-induced rise in net Na absorption and/or [Ca2+]i and/or 2) paucity of apical maxi-K channels. An approximately sixfold increase in tubular fluid flow rate in CCDs isolated from 4-wk-old rabbits and microperfused in vitro led to an increase in net Na absorption and [Ca2+]i, similar in magnitude to the response observed in 6-wk-old tubules, but it failed to generate an increase in net K secretion. By 5 wk of age, there was a small, but significant, flow-stimulated rise in net K secretion that increased further by 6 wk of life. Luminal perfusion with iberiotoxin blocked the flow stimulation of net K secretion in the adult CCD, confirming the identity of the maxi-K channel in this response. Maxi-K channel α-subunit message was consistently detected in single CCDs from animals ≥4 wk of age by RT-PCR. Indirect immunofluorescence microscopy using antibodies directed against the α-subunit revealed apical labeling of intercalated cells in cryosections from animals ≥5 wk of age; principal cell labeling was generally intracellular and punctate. We speculate that the postnatal appearance of flow-dependent K secretion is determined by the transcriptional/translational regulation of expression of maxi-K channels. Furthermore, our studies suggest a novel function for intercalated cells in mediating flow-stimulated K secretion.

Sign in / Sign up

Export Citation Format

Share Document