Expression of TWIK-1, a novel weakly inward rectifying potassium channel in rat kidney.
Several K+ conductances have been identified in the kidney, with specific properties and localization in distinct cell types and membrane domains. On the other hand, several K+ channels have been characterized at the molecular level. By immunolocalization, we show that a new inward rectifying K+ channel, TWIK-1, is specifically expressed in distinct tubular segments and cell types of the rat kidney. In the proximal tubule, TWIK-1 prevails in the initial portions (convoluted part), where it is restricted to the apical (brush-border) membrane. In the collecting duct, immunofluorescence was intracellular or confined to the apical membrane and restricted to intercalated cells, i.e., in cells lacking aquaporin-2, as shown by double immunofluorescence. TWIK was also expressed in medullary and cortical parts of the thick limb of the loop of Henle, identified with an anti-Tamm-Horsfall protein antibody (double immunofluorescence). The intensity of TWIK-1 immunolabeling was unchanged in rats fed a low-Na+ or a low-K+ diet. Because TWIK-1 shares common properties with the low-conductance apical K+ channel of the collecting duct, we propose that it could play a role in K+ secretion, complementary to ROMK, another recently characterized K+ channel located in principal cells of the cortical collecting duct and in the loop of Henle.
Cluzeaud
F
F
Unité 478, Institut National de la Santé et de la Recherche Médicale, Faculté de Médecine X. Bichat, F-75870 Paris cedex 18, France.
Reyes
R
R
Escoubet
B
B
Fay
M
M
Lazdunski
M
M
Bonvalet
J P
JP
Lesage
F
F
Farman
N
N
D000818:Animals; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins / Q000378:metabolism; D015153:Blotting, Western; D019556:COS Cells / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism; D008138:Loop of Henle / Q000166:cytology / Q000378:metabolism; D008297:Male; D009088:Mucoproteins / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D024683:Potassium Channels, Tandem Pore Domain; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution; D058949:Uromodulin
C496025:Aqp2 protein, rat; D051399:Aquaporin 2; D051403:Aquaporin 6; D020346:Aquaporins; C487530:Kcnk1 protein, rat; D009088:Mucoproteins; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; C548614:Umod protein, rat; D058949:Uromodulin