Primary structure and functional expression of a cortical collecting duct K(ir) channel

Research output: Contribution to journalArticle

Abstract

Maintenance of a negative membrane potential in the cortical collecting duct (CCD) principal cell depends on a small-conductance, inward-rectifying basolateral membrane K+ (K(ir)) channel. In the present study, a candidate cDNA encoding this K+ channel, CCD-IRK3, was isolated from a mouse collecting duct cell line, M1. CCD-IRK3 shares a high degree of homology with a human brain inward-rectifier K+ channel (K(ir) 2.3). By Northern analysis, CCD-IRK3 transcript (2.9 kb) was readily detected in M1 CCD cells but not in Madin-Darby canine kidney, LLC-PK1, Chinese hamster ovary, or monkey kidney fibroblast cell lines. CCD-IRK3-specific reverse transcription-polymerase chain reaction confirmed bonafide expression in the kidney. Functional expression studies in Xenopus oocytes revealed that CCD- IRK3 operates as strongly inward-rectifying K+ channel. The cation selectivity profile of CCD-IRK3[ionic permeability values (P(K)/P(i)), Tl ≤ Rb ≤ K+ >> NH4 > Na; inward-slope conductance (G(K)/G(i)), Tl ≤ K+ >> NH4 > Na > Rb] is similiar to the macroscopic CCD basolateral membrane K+ conductance (G(K)/G(i), K+ >> NH4 > Rb; P(K)/P(i), Rb ≃ K+ >> NH4). CCD- IRK3 also exhibits the pharmacological features of the native channel. Patch-damp analysis reveals that CCD-IRK3 functions as a high open probability, voltage-independent, small-conductance channel (14.5 pS), consistent with the native channel. Based on these independent lines of evidence, CCD-IRK3 is a possible candidate for the small-conductance basolateral K(ir) channel in the CCD.

Original languageEnglish (US)
Pages (from-to)F825-F836
JournalAmerican Journal of Physiology - Renal Physiology
Volume273
Issue number5 42-5
StatePublished - Dec 9 1997
Externally publishedYes

Fingerprint

Kidney
Inwardly Rectifying Potassium Channel
Cell Line
Membranes
Xenopus
Cricetulus
Membrane Potentials
Reverse Transcription
Oocytes
Haplorhini
Cations
Canidae
Ovary
Permeability
Complementary DNA
Fibroblasts
Maintenance
Pharmacology
Polymerase Chain Reaction
Brain

Keywords

  • Epithelial transport
  • Fluid and electrolyte balance
  • Inward-rectifying potassium channel
  • Kidney

ASJC Scopus subject areas

  • Physiology
  • Urology

Cite this

Primary structure and functional expression of a cortical collecting duct K(ir) channel. / Welling, Paul A.

In: American Journal of Physiology - Renal Physiology, Vol. 273, No. 5 42-5, 09.12.1997, p. F825-F836.

Research output: Contribution to journalArticle

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