Primary structure and functional expression of a cortical collecting duct Kir channel.
Primary structure and functional expression of a cortical collecting duct Kir channel.
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DOI：
10.1152/ajprenal.1997.273.5.f825
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发表时间：
1997-11
期刊：
影响因子：
--
通讯作者：
P. Welling
中科院分区：
文献类型：
--
作者：
P. Welling
Maintenance of a negative membrane potential in the cortical collecting duct (CCD) principal cell depends on a small-conductance, inward-rectifying basolateral membrane K+(Kir) 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 (Kir 2.3). By Northern analysis, CCD-IRK3transcript (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-clamp 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 Kir channel in the CCD.
