TY - JOUR

T1 - Calmodulin is essential for cardiac IKS channel gating and assembly: impaired function in long-QT mutations.

AU - Shamgar, Liora

AU - Ma, Lijuan

AU - Schmitt, Nicole

AU - Haitin, Yoni

AU - Peretz, Asher

AU - Wiener, Reuven

AU - Hirsch, Joel

AU - Pongs, Olaf

AU - Attali, Bernard

N1 - Keywords: Animals; CHO Cells; Calmodulin; Cricetinae; Humans; Ion Channel Gating; KCNQ1 Potassium Channel; Long QT Syndrome; Patch-Clamp Techniques; Potassium Channels, Voltage-Gated; Protein Folding; Transfection

PY - 2006

Y1 - 2006

N2 - The slow IKS K+ channel plays a major role in repolarizing the cardiac action potential and consists of the assembly of KCNQ1 and KCNE1 subunits. Mutations in either KCNQ1 or KCNE1 genes produce the long-QT syndrome, a life-threatening ventricular arrhythmia. Here, we show that long-QT mutations located in the KCNQ1 C terminus impair calmodulin (CaM) binding, which affects both channel gating and assembly. The mutations produce a voltage-dependent macroscopic inactivation and dramatically alter channel assembly. KCNE1 forms a ternary complex with wild-type KCNQ1 and Ca(2+)-CaM that prevents inactivation, facilitates channel assembly, and mediates a Ca(2+)-sensitive increase of IKS-current, with a considerable Ca(2+)-dependent left-shift of the voltage-dependence of activation. Coexpression of KCNQ1 or IKS channels with a Ca(2+)-insensitive CaM mutant markedly suppresses the currents and produces a right shift in the voltage-dependence of channel activation. KCNE1 association to KCNQ1 long-QT mutants significantly improves mutant channel expression and prevents macroscopic inactivation. However, the marked right shift in channel activation and the subsequent decrease in current amplitude cannot restore normal levels of IKS channel activity. Our data indicate that in healthy individuals, CaM binding to KCNQ1 is essential for correct channel folding and assembly and for conferring Ca(2+)-sensitive IKS-current stimulation, which increases the cardiac repolarization reserve and hence prevents the risk of ventricular arrhythmias. Udgivelsesdato: 2006-Apr-28

AB - The slow IKS K+ channel plays a major role in repolarizing the cardiac action potential and consists of the assembly of KCNQ1 and KCNE1 subunits. Mutations in either KCNQ1 or KCNE1 genes produce the long-QT syndrome, a life-threatening ventricular arrhythmia. Here, we show that long-QT mutations located in the KCNQ1 C terminus impair calmodulin (CaM) binding, which affects both channel gating and assembly. The mutations produce a voltage-dependent macroscopic inactivation and dramatically alter channel assembly. KCNE1 forms a ternary complex with wild-type KCNQ1 and Ca(2+)-CaM that prevents inactivation, facilitates channel assembly, and mediates a Ca(2+)-sensitive increase of IKS-current, with a considerable Ca(2+)-dependent left-shift of the voltage-dependence of activation. Coexpression of KCNQ1 or IKS channels with a Ca(2+)-insensitive CaM mutant markedly suppresses the currents and produces a right shift in the voltage-dependence of channel activation. KCNE1 association to KCNQ1 long-QT mutants significantly improves mutant channel expression and prevents macroscopic inactivation. However, the marked right shift in channel activation and the subsequent decrease in current amplitude cannot restore normal levels of IKS channel activity. Our data indicate that in healthy individuals, CaM binding to KCNQ1 is essential for correct channel folding and assembly and for conferring Ca(2+)-sensitive IKS-current stimulation, which increases the cardiac repolarization reserve and hence prevents the risk of ventricular arrhythmias. Udgivelsesdato: 2006-Apr-28

U2 - 10.1161/01.RES.0000218979.40770.69

DO - 10.1161/01.RES.0000218979.40770.69

M3 - Journal article

C2 - 16556865

VL - 98

SP - 1055

EP - 1063

JO - Circulation Research

JF - Circulation Research

SN - 0009-7330

IS - 8

ER -