AJP - Renal Physiology, Vol 273, Issue 4 663-F666, Copyright © 1997 by American Physiological Society

ARTICLES

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

M. Orias, H. Velazquez, F. Tung, G. Lee and G. V. Desir
Department of Medicine, Yale University School of Medicine and Department of Veterans Affairs Medical Center, New Haven, Connecticut 06510, USA.

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.

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