TY - JOUR
T1 - Functional modulation of the transient outward current Ito by KCNE β-subunits and regional distribution in human non-failing and failing hearts
AU - Radicke, Susanne
AU - Cotella, Diego
AU - Graf, Eva Maria
AU - Banse, Ulrich
AU - Jost, Norbert
AU - Varró, András
AU - Tseng, Gea Ny
AU - Ravens, Ursula
AU - Wettwer, Erich
N1 - Funding Information:
This work was supported by the MeDDrive 2001 of the Medical Faculty, Dresden University of Technology, Dresden, Germany and by the European Commission, Marie Curie Development Host Fellowship, Contract No.: HPMD-CT-2001-00119. We would like to thank Mrs. Fischer and Mrs. Schöne for their excellent technical assistance. We acknowledge the great help and cooperation of the surgeons of the Dresden Heart Centre (Drs. M. Knaut, K. Matschke, R. Cichon, U. Kappert, M. Tugtekin). We also want to thank Dr. T. Christ for his indispensable assistance and helpful discussion.
PY - 2006/9/1
Y1 - 2006/9/1
N2 - Objectives: The function of Kv4.3 (KCND3) channels, which underlie the transient outward current Ito in human heart, can be modulated by several accessory subunits such as KChIP2 and KCNE1-KCNE5. Here we aimed to determine the regional expression of Kv4.3, KChIP2, and KCNE mRNAs in non-failing and failing human hearts and to investigate the functional consequences of subunit coexpression in heterologous expression systems. Methods: We quantified mRNA levels for two Kv4.3 isoforms, Kv4.3-S and Kv4.3-L, and for KChIP2 as well as KCNE1-KCNE5 with real-time RT-PCR. We also studied the effects of KCNEs on Kv4.3 + KChIP2 current characteristics in CHO cells with the whole-cell voltage-clamp method. Results: In non-failing hearts, low expression was found for KCNE1, KCNE3, and KCNE5, three times higher expression for KCNE2, and 60 times higher for KCNE4. Transmural gradients were detected only for KChIP2 in left and right ventricles. Compared to non-failing tissue, failing hearts showed higher expression of Kv4.3-L and KCNE1 and lower of Kv4.3-S, KChIP2, KCNE4, and KCNE5. In CHO cells, Kv4.3 + KChIP2 currents were differentially modified by co-expressed KCNEs: time constants of inactivation were shorter with KCNE1 and KCNE3-5 while time-to-peak was decreased, and V0.5 of steady-state inactivation was shifted to more negative potentials by all KCNE subunits. Importantly, KCNE2 induced a unique and prominent 'overshoot' of peak current during recovery from inactivation similar to that described for human Ito while other KCNE subunits induced little (KCNE4,5) or no overshoot. Conclusions: All KCNEs are expressed in the human heart at the transcript level. Compared to Ito in native human myocytes, none of the combination of KChIP2 and KCNE produced an ideal congruency in current characteristics, suggesting that additional factors contribute to the regulation of the native Ito channel.
AB - Objectives: The function of Kv4.3 (KCND3) channels, which underlie the transient outward current Ito in human heart, can be modulated by several accessory subunits such as KChIP2 and KCNE1-KCNE5. Here we aimed to determine the regional expression of Kv4.3, KChIP2, and KCNE mRNAs in non-failing and failing human hearts and to investigate the functional consequences of subunit coexpression in heterologous expression systems. Methods: We quantified mRNA levels for two Kv4.3 isoforms, Kv4.3-S and Kv4.3-L, and for KChIP2 as well as KCNE1-KCNE5 with real-time RT-PCR. We also studied the effects of KCNEs on Kv4.3 + KChIP2 current characteristics in CHO cells with the whole-cell voltage-clamp method. Results: In non-failing hearts, low expression was found for KCNE1, KCNE3, and KCNE5, three times higher expression for KCNE2, and 60 times higher for KCNE4. Transmural gradients were detected only for KChIP2 in left and right ventricles. Compared to non-failing tissue, failing hearts showed higher expression of Kv4.3-L and KCNE1 and lower of Kv4.3-S, KChIP2, KCNE4, and KCNE5. In CHO cells, Kv4.3 + KChIP2 currents were differentially modified by co-expressed KCNEs: time constants of inactivation were shorter with KCNE1 and KCNE3-5 while time-to-peak was decreased, and V0.5 of steady-state inactivation was shifted to more negative potentials by all KCNE subunits. Importantly, KCNE2 induced a unique and prominent 'overshoot' of peak current during recovery from inactivation similar to that described for human Ito while other KCNE subunits induced little (KCNE4,5) or no overshoot. Conclusions: All KCNEs are expressed in the human heart at the transcript level. Compared to Ito in native human myocytes, none of the combination of KChIP2 and KCNE produced an ideal congruency in current characteristics, suggesting that additional factors contribute to the regulation of the native Ito channel.
KW - Gene expression
KW - Heart failure
KW - K-channel
KW - Membrane currents
KW - Ventricular function
UR - https://www.scopus.com/pages/publications/33751569719
U2 - 10.1016/j.cardiores.2006.06.017
DO - 10.1016/j.cardiores.2006.06.017
M3 - Article
SN - 0008-6363
VL - 71
SP - 695
EP - 703
JO - Cardiovascular Research
JF - Cardiovascular Research
IS - 4
ER -