In vitro molecular interactions and distribution of KCNE family with KCNQ1 in the human heart.
OBJECTIVE
The voltage-gated K+ channel KCNQ1 associates with the small KCNE1 beta subunit to underlie the IKs repolarizing current in the heart. Based on sequence homology, the KCNE family is recognized to comprise five members. Controversial data have indicated their participation in several K+ channel protein complexes, including KCNQ1. The expression level and the putative functions of the different KCNE subunits in the human heart still require further investigation.


METHODS
We have carried out a comparative study of all KCNE subunits with KCNQ1 using the patch-clamp technique in mammalian cells. Real-time RT-PCR absolute quantification was performed on human atrial and ventricular tissue.


RESULTS
While KCNQ1/KCNE1 heteromultimer reached high current density with slow gating kinetics and pronounced voltage dependence, KCNQ1/KCNE2 and KCNQ1/KCNE3 complexes produced instantaneous voltage-independent currents with low and high current density, respectively. Co-expression of KCNE4 or KCNE5 with KCNQ1 induced small currents in the physiological range of voltages, with kinetics similar to those of the KCNQ1/KCNE1 complex. However, co-expression of these inhibitory subunits with a disease-associated mutation (S140G-KCNQ1) led to currents that were almost undistinguishable from the KCNQ1/KCNE1 canonical complex. Absolute cDNA quantification revealed a relatively homogeneous distribution of each transcript, except for KCNE4, inside left atria and endo- and epicardia of left ventricular wall with the following abundance: KCNQ1 >> KCNE4 > or = KCNE1 > KCNE3 > KCNE2 > KCNE5. KCNE4 expression was twice as high in atrium compared to ventricle.


CONCLUSIONS
Our data show that KCNQ1 forms a channel complex with 5 KCNE subunits in a specific manner but only interactions with KCNE1, KCNE2, and KCNE3 may have physiological relevance in the human heart.
Bendahhou
Saïd
S
Institut de Pharmacologie Moléculaire et Cellulaire, UMR 6097 CNRS and Université de Nice Sophia Antipolis, 660 Route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France. bendahhou@ipmc.cnrs.fr
Marionneau
Céline
C
Haurogne
Karinne
K
Larroque
Marie-Madeleine
MM
Derand
Renaud
R
Szuts
Viktoria
V
Escande
Denis
D
Demolombe
Sophie
S
Barhanin
Jacques
J
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006224:Cricetinae; D006325:Heart Atria; D006801:Humans; D015640:Ion Channel Gating; D051657:KCNQ1 Potassium Channel / Q000235:genetics*; D009206:Myocardium / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection / Q000379:methods
C489622:KCNE1 protein, human; C489619:KCNE2 protein, human; C418492:KCNE3 protein, human; C498897:KCNE4 protein, human; C502068:KCNE5 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger