Dynamic partnership between KCNQ1 and KCNE1 and influence on cardiac IKs current amplitude by KCNE2.
Cardiac slow delayed rectifier (IKs) channel is composed of KCNQ1 (pore-forming) and KCNE1 (auxiliary) subunits. Although KCNE1 is an obligate IKs component that confers the uniquely slow gating kinetics, KCNE2 is also expressed in human heart. In vitro experiments suggest that KCNE2 can associate with the KCNQ1-KCNE1 complex to suppress the current amplitude without altering the slow gating kinetics. Our goal here is to test the role of KCNE2 in cardiac IKs channel function. Pulse-chase experiments in COS-7 cells show that there is a KCNE1 turnover in the KCNQ1-KCNE1 complex, supporting the possibility that KCNE1 in the IKs channel complex can be substituted by KCNE2 when the latter is available. Biotinylation experiments in COS-7 cells show that although KCNE1 relies on KCNQ1 coassembly for more efficient cell surface expression, KCNE2 can independently traffic to the cell surface, thus becoming available for substituting KCNE1 in the IKs channel complex. Injecting vesicles carrying KCNE1 or KCNE2 into KCNQ1-expressing oocytes leads to KCNQ1 modulation in the same manner as KCNQ1+KCNEx (where x=1 or 2) cRNA coinjection. Thus, free KCNEx peptides delivered to the cell membrane can associate with existing KCNQ1 channels to modulate their function. Finally, adenovirus-mediated KCNE2 expression in adult guinea pig ventricular myocytes exhibited colocalization with native KCNQ1 protein and reduces the native IKs current density. We propose that in cardiac myocytes the IKs current amplitude is under dynamic control by the availability of KCNE2 subunits in the cell membrane.
From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298.
Min
M
Jiang
From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298.
Xulin
X
Xu
From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298.
Yuhong
Y
Wang
Department of Physiology, Shiga University of Medical Science, Shiga 520-2192, Japan.
Futoshi
F
Toyoda
From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298.
Xian-Sheng
XS
Liu
From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298.
Mei
M
Zhang
Department of Pharmacology and Center for Molecular Therapeutics, Columbia University, New York, New York 10032.
Richard B
RB
Robinson
From the Department of Physiology & Biophysics, Virginia Commonwealth University, Richmond, Virginia 23298. Electronic address: gtseng@vcu.edu.
Gea-Ny
GN
Tseng
D000200:Action Potentials / Q000502:physiology; D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D019921:Biotinylation; D019556:COS Cells; D002522:Chlorocebus aethiops; D015870:Gene Expression / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006168:Guinea Pigs; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D011956:Receptors, Cell Surface / Q000502:physiology; D051672:Shal Potassium Channels / Q000502:physiology
C489622:KCNE1 protein, human; C489619:KCNE2 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D011956:Receptors, Cell Surface; D051672:Shal Potassium Channels; D049452:Green Fluorescent Proteins; D011188:Potassium