Cloning and function of the rat colonic epithelial K+ channel KVLQT1.
KVLQT1 (KCNQ1) is a voltage-gated K+ channel essential for repolarization of the heart action potential that is defective in cardiac arrhythmia. The channel is inhibited by the chromanol 293B, a compound that blocks cAMP-dependent electrolyte secretion in rat and human colon, therefore suggesting expression of a similar type of K+ channel in the colonic epithelium. We now report cloning and expression of KVLQT1 from rat colon. Overlapping clones identified by cDNA-library screening were combined to a full length cDNA that shares high sequence homology to KVLQT1 cloned from other species. RT-PCR analysis of rat colonic musoca demonstrated expression of KVLQT1 in crypt cells and surface epithelium. Expression of rKVLQT1 in Xenopus oocytes induced a typical delayed activated K+ current, that was further activated by increase of intracellular cAMP but not Ca2+ and that was blocked by the chromanol 293B. The same compound blocked a basolateral cAMP-activated K+ conductance in the colonic mucosal epithelium and inhibited whole cell K+ currents in patch-clamp experiments on isolated colonic crypts. We conclude that KVLQT1 is forming an important component of the basolateral cAMP-activated K+ conductance in the colonic epithelium and plays a crucial role in diseases like secretory diarrhea and cystic fibrosis.
Kunzelmann
K
K
Department of Physiology & Pharmacology, University of Queensland St Lucia, Brisbane, Australia.
Hübner
M
M
Schreiber
R
R
Levy-Holzman
R
R
Garty
H
H
Bleich
M
M
Warth
R
R
Slavik
M
M
von Hahn
T
T
Greger
R
R
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002316:Cardiotonic Agents / Q000494:pharmacology; D003001:Cloning, Molecular; D005576:Colforsin / Q000494:pharmacology; D003106:Colon / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008297:Male; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D019789:Tetraethylammonium / Q000494:pharmacology; D014982:Xenopus laevis
D002316:Cardiotonic Agents; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; C496911:Kcnq1 protein, rat; D010726:Phosphodiesterase Inhibitors; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D005576:Colforsin; D001464:Barium; D019789:Tetraethylammonium; D002217:Carbachol; D000242:Cyclic AMP; D015232:Dinoprostone; D015056:1-Methyl-3-isobutylxanthine