Protein kinase G activates inwardly rectifying K+ channel in cultured human proximal tubule cells

2002 ◽  
Vol 283 (4) ◽  
pp. F784-F791 ◽  
Author(s):  
Kazuyoshi Nakamura ◽  
Junko Hirano ◽  
Shun-Ichi Itazawa ◽  
Manabu Kubokawa
Keyword(s):  
Proximal Tubule ◽  
Specific Inhibitor ◽  
K Channel ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Proximal Tubule Cells ◽  
Bath Application ◽  
Tubule Cells ◽  
Inwardly Rectifying ◽  
Human Proximal Tubule

An ATP-regulated inwardly rectifying K+ channel, whose activity is enhanced by PKA, is present in the plasma membrane of cultured human proximal tubule cells. In this study, we investigated the effects of PKG on this K+ channel, using the patch-clamp technique. In cell-attached patches, bath application of a membrane-permeant cGMP analog, 8-bromoguanosine 3′,5′-monophosphate (8-BrcGMP; 100 μM), stimulated channel activity, whereas application of a PKG-specific inhibitor, KT-5823 (1 μM), reduced the activity. Channel activation induced by 8-BrcGMP was observed even in the presence of a PKA-specific inhibitor, KT-5720 (500 nM), which was abolished by KT-5823. Direct effects of cGMP and PKG were examined with inside-out patches in the presence of 1 mM MgATP. Although cytoplasmic cGMP (100 μM) alone had little effect on channel activity, subsequent addition of PKG (500 U/ml) enhanced it. Furthermore, bath application of atrial natriuretic peptide (ANP; 20 nM) in cell-attached patches stimulated channel activity, which was blocked by KT-5823. In conclusion, cGMP/PKG-dependent processes participate in activating the ATP-regulated K+ channel and producing the stimulatory effect of ANP on channel activity.

scholarly journals Involvement of Endogenous Nitric Oxide in the Regulation of K+ Channel Activity in Cultured Human Proximal Tubule Cells

2006 ◽  
Vol 56 (6) ◽  
pp. 407-413 ◽  
Author(s):  
Kazuyoshi Nakamura ◽  
Wataru Habano ◽  
Toshiyuki Kojo ◽  
You Komagiri ◽  
Takahiro Kubota ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Proximal Tubule ◽  
K Channel ◽  
Channel Activity ◽  
Proximal Tubule Cells ◽  
Endogenous Nitric Oxide ◽  
Tubule Cells ◽  
Human Proximal Tubule

scholarly journals Proinflammatory Cytokines and Potassium Channels in the Kidney

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Kazuyoshi Nakamura ◽  
Hikaru Hayashi ◽  
Manabu Kubokawa
Keyword(s):  
Proximal Tubule ◽  
Proinflammatory Cytokines ◽  
Transforming Growth Factor ◽  
Interleukin 1 ◽  
Transepithelial Transport ◽  
Channel Activity ◽  
Proximal Tubule Cells ◽  
Cell Functions ◽  
Tubule Cells ◽  
Human Proximal Tubule

Proinflammatory cytokines affect several cell functions via receptor-mediated processes. In the kidney, functions of transporters and ion channels along the nephron are also affected by some cytokines. Among these, alteration of activity of potassium ion (K+) channels induces changes in transepithelial transport of solutes and water in the kidney, since K+channels in tubule cells are indispensable for formation of membrane potential which serves as a driving force for the transepithelial transport. Altered K+channel activity may be involved in renal cell dysfunction during inflammation. Although little information was available regarding the effects of proinflammatory cytokines on renal K+channels, reports have emerged during the last decade. In human proximal tubule cells, interferon-γshowed a time-dependent biphasic effect on a 40 pS K+channel, that is, delayed suppression and acute stimulation, and interleukin-1βacutely suppressed the channel activity. Transforming growth factor-β1 activated KCa3.1 K+channel in immortalized human proximal tubule cells, which would be involved in the pathogenesis of renal fibrosis. This review discusses the effects of proinflammatory cytokines on renal K+channels and the causal relationship between the cytokine-induced changes in K+channel activity and renal dysfunction.

scholarly journals Activation of Inwardly Rectifying K+ Channel in OK Proximal Tubule Cells Involves cGMP-Dependent Phosphorylation Process.

1998 ◽  
Vol 48 (6) ◽  
pp. 467-476 ◽  
Author(s):  
Manabu KUBOKAWA ◽  
Shigeyuki NAKAYA ◽  
Yoshichika YOSHIOKA ◽  
Kazuyoshi NAKAMURA ◽  
Fumio SATO ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
K Channel ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Inwardly Rectifying

Regulation of an inwardly rectifying K+ channel by nitric oxide in cultured human proximal tubule cells

2004 ◽  
Vol 287 (3) ◽  
pp. F411-F417 ◽  
Author(s):  
Kazuyoshi Nakamura ◽  
Junko Hirano ◽  
Manabu Kubokawa
Keyword(s):  
Nitric Oxide ◽  
Protein Kinase ◽  
Low Dose ◽  
Specific Inhibitor ◽  
High Dose ◽  
Channel Activity ◽  
No Donor ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Inwardly Rectifying

We investigated the effects of nitric oxide (NO) on activity of the inwardly rectifying K+ channel in cultured human proximal tubule cells, using the cell-attached mode of the patch-clamp technique. An inhibitor of NO synthases, Nω-nitro-l-arginine methyl ester (l-NAME; 100 μM), reduced channel activity, which was restored by an NO donor, sodium nitroprusside (SNP; 10 μM) or 8-bromo-cGMP (8-BrcGMP; 100 μM). However, SNP failed to activate the channel in the presence of an inhibitor of soluble guanylate cyclase, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 μM). Similarly, the SNP effect was abolished by a protein kinase G (PKG)-specific inhibitor, KT-5823 (1 μM), but not by a protein kinase A-specific inhibitor, KT-5720 (500 nM). Another NO donor, S-nitroso- N-acetyl-d,l-penicillamine (10 μM), mimicked the SNP-induced channel activation. In contrast to the stimulatory effect of SNP at a low dose (10 μM), a higher dose of SNP (1 mM) reduced channel activity, which was not restored by 8-BrcGMP. Recordings of membrane potential with the slow whole cell configuration demonstrated that l-NAME (100 μM) and the high dose of SNP (1 mM) depolarized the cell by 10.1 ± 2.6 and 9.2 ± 1.0 mV, respectively, whereas the low dose of SNP (10 μM) hyperpolarized it by 7.1 ± 0.7 mV. These results suggested that the endogenous NO would contribute to the maintenance of basal activity of this K+ channel and hence the potential formation via a cGMP/PKG-dependent mechanism, whereas a high dose of NO impaired channel activity independent of cGMP/PKG-mediated processes.

scholarly journals Properties of an Inwardly Rectifying ATP-sensitive K+ Channel in the Basolateral Membrane of Renal Proximal Tubule

1998 ◽  
Vol 111 (1) ◽  
pp. 139-160 ◽  
Author(s):  
Ulrich R. Mauerer ◽  
Emile L. Boulpaep ◽  
Alan S. Segal
Keyword(s):  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Potassium Conductance ◽  
Physiological Role ◽  
K Channel ◽  
Nucleoside Triphosphate ◽  
Channel Activity ◽  
Open Probability ◽  
Proximal Tubule Cells ◽  
Tubule Cells

The potassium conductance of the basolateral membrane (BLM) of proximal tubule cells is a critical regulator of transport since it is the major determinant of the negative cell membrane potential and is necessary for pump-leak coupling to the Na+,K+-ATPase pump. Despite this pivotal physiological role, the properties of this conductance have been incompletely characterized, in part due to difficulty gaining access to the BLM. We have investigated the properties of this BLM K+ conductance in dissociated, polarized Ambystoma proximal tubule cells. Nearly all seals made on Ambystoma cells contained inward rectifier K+ channels (γslope, in = 24.5 ± 0.6 pS, γchord, out = 3.7 ± 0.4 pS). The rectification is mediated in part by internal Mg2+. The open probability of the channel increases modestly with hyperpolarization. The inward conducting properties are described by a saturating binding–unbinding model. The channel conducts Tl+ and K+, but there is no significant conductance for Na+, Rb+, Cs+, Li+, NH4+, or Cl−. The channel is inhibited by barium and the sulfonylurea agent glibenclamide, but not by tetraethylammonium. Channel rundown typically occurs in the absence of ATP, but cytosolic addition of 0.2 mM ATP (or any hydrolyzable nucleoside triphosphate) sustains channel activity indefinitely. Phosphorylation processes alone fail to sustain channel activity. Higher doses of ATP (or other nucleoside triphosphates) reversibly inhibit the channel. The K+ channel opener diazoxide opens the channel in the presence of 0.2 mM ATP, but does not alleviate the inhibition of millimolar doses of ATP. We conclude that this K+ channel is the major ATP-sensitive basolateral K+ conductance in the proximal tubule.

Delayed and acute effects of interferon-γ on activity of an inwardly rectifying K+ channel in cultured human proximal tubule cells

2009 ◽  
Vol 296 (1) ◽  
pp. F46-F53 ◽  
Author(s):  
Kazuyoshi Nakamura ◽  
You Komagiri ◽  
Toshiyuki Kojo ◽  
Manabu Kubokawa
Keyword(s):  
Proximal Tubule ◽  
Acute Effect ◽  
No Production ◽  
Channel Activity ◽  
Acute Effects ◽  
Prolonged Incubation ◽  
Proximal Tubule Cells ◽  
Ifn Γ ◽  
Tubule Cells ◽  
Inwardly Rectifying

The activity of an inwardly rectifying K+ channel in cultured human renal proximal tubule cells (RPTECs) is stimulated and inhibited by nitric oxide (NO) at low and high concentrations, respectively. In this study, we investigated the effects of IFN-γ, one of the cytokines which affect the expression of inducible NO synthase (iNOS), on intracellular NO and channel activity of RPTECs, using RT-PCR, NO imaging, and the cell-attached mode of the patch-clamp technique. Prolonged incubation (24 h) of cells with IFN-γ (20 ng/ml) enhanced iNOS mRNA expression and NO production. In these cells, a NOS inhibitor, Nω-nitro-l-arginine methyl ester (l-NAME; 100 μM), elevated channel activity, suggesting that NO production was so high as to suppress the channel. This indicated that IFN-γ would chronically suppress channel activity by enhancing NO production. Acute effects of IFN-γ was also examined in control cells. Simple addition of IFN-γ (20 ng/ml) to the bath acutely stimulated channel activity, which was abolished by inhibitors of IFN-γ receptor-associated Janus-activated kinase [P6 (1 μM) and AG490 (10 μM)]. However, l-NAME did not block the acute effect of IFN-γ. Indeed, IFN-γ did not acutely affect NO production. Moreover, the acute effect was not blocked by inhibition of PKA, PKG, and phosphatidylinositol 3-kinase (PI3K). We conclude that IFN-γ exerted a delayed suppressive effect on K+ channel activity by enhancing iNOS expression and an acute stimulatory effect, which was independent of either NO pathways or phosphorylation processes mediated by PKA, PKG, and PI3K in RPTECs.

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