Modulation of the Ca2+-activated large conductance K+ channel by intracellular pH in human renal proximal tubule cells

Junko Hirano, Kazuyoshi Nakamura, Shun Ichi Itazawa, Yoshiro Sohma, Takahiro Kubota, Manabu Kubokawa

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The Ca2+-activated and voltage-sensitive large conductance K- channel (BK channel) with a slope conductance of about 300 pS is present in the surface membrane of cultured human renal proximal tubule epithelial cells (RPTECs). In this study we examined the effects of cytoplasmic pH (pHi) on activity and gating kinetics of the BK channel by using the inside-out configuration of the patch-clamp technique. At a constant cytoplasmic Ca2- concentration ([Ca2-]i), membrane depolarization raised channel open probability (Po), and lowering pHi shifted the Po-membrane potential (Vm) relationship to the positive voltage direction. However, the value of the gating charge was not affected by changes in pHi, suggesting that the effects of pHi on Po were not due to an alternation of the voltage sensitivity. At constant Vm, lowering pHi suppressed the [Ca2+]i-dependent channel activation and shifted the Po-[Ca2+]i relationship in the direction of higher [Ca2-]i with a reduction of maximal Po. Furthermore, both the mean open and mean closed times of the BK channels at pHi 6.3 in the presence of 10-4M [Ca2-]i were shorter than those at pHi 7.3 in the presence of 10-5 M [Ca2+]i, even though these two different conditions gave a similar Po. The data indicate that cytoplasmic H- suppresses Po of the BK channel in RPTECs, which involves the mechanism independent of Ca2+ activation. Our preliminary kinetic analysis also supported this notion.

Original languageEnglish
Pages (from-to)267-276
Number of pages10
JournalJapanese Journal of Physiology
Volume52
Issue number3
DOIs
Publication statusPublished - 2002 Jun
Externally publishedYes

Fingerprint

Proximal Kidney Tubule
Large-Conductance Calcium-Activated Potassium Channels
Epithelial Cells
Membranes
Patch-Clamp Techniques
Membrane Potentials

Keywords

  • Channel activity
  • Gating kinetics
  • Intracellular pH
  • Kidney

ASJC Scopus subject areas

  • Physiology

Cite this

Modulation of the Ca2+-activated large conductance K+ channel by intracellular pH in human renal proximal tubule cells. / Hirano, Junko; Nakamura, Kazuyoshi; Itazawa, Shun Ichi; Sohma, Yoshiro; Kubota, Takahiro; Kubokawa, Manabu.

In: Japanese Journal of Physiology, Vol. 52, No. 3, 06.2002, p. 267-276.

Research output: Contribution to journalArticle

Hirano, Junko ; Nakamura, Kazuyoshi ; Itazawa, Shun Ichi ; Sohma, Yoshiro ; Kubota, Takahiro ; Kubokawa, Manabu. / Modulation of the Ca2+-activated large conductance K+ channel by intracellular pH in human renal proximal tubule cells. In: Japanese Journal of Physiology. 2002 ; Vol. 52, No. 3. pp. 267-276.
@article{cfdcc8128ff640de846c4644ce93cd0f,
title = "Modulation of the Ca2+-activated large conductance K+ channel by intracellular pH in human renal proximal tubule cells",
abstract = "The Ca2+-activated and voltage-sensitive large conductance K- channel (BK channel) with a slope conductance of about 300 pS is present in the surface membrane of cultured human renal proximal tubule epithelial cells (RPTECs). In this study we examined the effects of cytoplasmic pH (pHi) on activity and gating kinetics of the BK channel by using the inside-out configuration of the patch-clamp technique. At a constant cytoplasmic Ca2- concentration ([Ca2-]i), membrane depolarization raised channel open probability (Po), and lowering pHi shifted the Po-membrane potential (Vm) relationship to the positive voltage direction. However, the value of the gating charge was not affected by changes in pHi, suggesting that the effects of pHi on Po were not due to an alternation of the voltage sensitivity. At constant Vm, lowering pHi suppressed the [Ca2+]i-dependent channel activation and shifted the Po-[Ca2+]i relationship in the direction of higher [Ca2-]i with a reduction of maximal Po. Furthermore, both the mean open and mean closed times of the BK channels at pHi 6.3 in the presence of 10-4M [Ca2-]i were shorter than those at pHi 7.3 in the presence of 10-5 M [Ca2+]i, even though these two different conditions gave a similar Po. The data indicate that cytoplasmic H- suppresses Po of the BK channel in RPTECs, which involves the mechanism independent of Ca2+ activation. Our preliminary kinetic analysis also supported this notion.",
keywords = "Channel activity, Gating kinetics, Intracellular pH, Kidney",
author = "Junko Hirano and Kazuyoshi Nakamura and Itazawa, {Shun Ichi} and Yoshiro Sohma and Takahiro Kubota and Manabu Kubokawa",
year = "2002",
month = "6",
doi = "10.2170/jjphysiol.52.267",
language = "English",
volume = "52",
pages = "267--276",
journal = "Journal of Physiological Sciences",
issn = "1880-6546",
publisher = "Springer Japan",
number = "3",

}

TY - JOUR

T1 - Modulation of the Ca2+-activated large conductance K+ channel by intracellular pH in human renal proximal tubule cells

AU - Hirano, Junko

AU - Nakamura, Kazuyoshi

AU - Itazawa, Shun Ichi

AU - Sohma, Yoshiro

AU - Kubota, Takahiro

AU - Kubokawa, Manabu

PY - 2002/6

Y1 - 2002/6

N2 - The Ca2+-activated and voltage-sensitive large conductance K- channel (BK channel) with a slope conductance of about 300 pS is present in the surface membrane of cultured human renal proximal tubule epithelial cells (RPTECs). In this study we examined the effects of cytoplasmic pH (pHi) on activity and gating kinetics of the BK channel by using the inside-out configuration of the patch-clamp technique. At a constant cytoplasmic Ca2- concentration ([Ca2-]i), membrane depolarization raised channel open probability (Po), and lowering pHi shifted the Po-membrane potential (Vm) relationship to the positive voltage direction. However, the value of the gating charge was not affected by changes in pHi, suggesting that the effects of pHi on Po were not due to an alternation of the voltage sensitivity. At constant Vm, lowering pHi suppressed the [Ca2+]i-dependent channel activation and shifted the Po-[Ca2+]i relationship in the direction of higher [Ca2-]i with a reduction of maximal Po. Furthermore, both the mean open and mean closed times of the BK channels at pHi 6.3 in the presence of 10-4M [Ca2-]i were shorter than those at pHi 7.3 in the presence of 10-5 M [Ca2+]i, even though these two different conditions gave a similar Po. The data indicate that cytoplasmic H- suppresses Po of the BK channel in RPTECs, which involves the mechanism independent of Ca2+ activation. Our preliminary kinetic analysis also supported this notion.

AB - The Ca2+-activated and voltage-sensitive large conductance K- channel (BK channel) with a slope conductance of about 300 pS is present in the surface membrane of cultured human renal proximal tubule epithelial cells (RPTECs). In this study we examined the effects of cytoplasmic pH (pHi) on activity and gating kinetics of the BK channel by using the inside-out configuration of the patch-clamp technique. At a constant cytoplasmic Ca2- concentration ([Ca2-]i), membrane depolarization raised channel open probability (Po), and lowering pHi shifted the Po-membrane potential (Vm) relationship to the positive voltage direction. However, the value of the gating charge was not affected by changes in pHi, suggesting that the effects of pHi on Po were not due to an alternation of the voltage sensitivity. At constant Vm, lowering pHi suppressed the [Ca2+]i-dependent channel activation and shifted the Po-[Ca2+]i relationship in the direction of higher [Ca2-]i with a reduction of maximal Po. Furthermore, both the mean open and mean closed times of the BK channels at pHi 6.3 in the presence of 10-4M [Ca2-]i were shorter than those at pHi 7.3 in the presence of 10-5 M [Ca2+]i, even though these two different conditions gave a similar Po. The data indicate that cytoplasmic H- suppresses Po of the BK channel in RPTECs, which involves the mechanism independent of Ca2+ activation. Our preliminary kinetic analysis also supported this notion.

KW - Channel activity

KW - Gating kinetics

KW - Intracellular pH

KW - Kidney

UR - http://www.scopus.com/inward/record.url?scp=0036592067&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0036592067&partnerID=8YFLogxK

U2 - 10.2170/jjphysiol.52.267

DO - 10.2170/jjphysiol.52.267

M3 - Article

C2 - 12230803

AN - SCOPUS:0036592067

VL - 52

SP - 267

EP - 276

JO - Journal of Physiological Sciences

JF - Journal of Physiological Sciences

SN - 1880-6546

IS - 3

ER -