Arrhythmogenic calmodulin mutations impede activation of small-conductance calcium-activated potassium current

作者：Yu Chih Chieh; Ko Jum Suk; Ai Tomohiko; Tsai Wen Chin; Chen Zhenhui; Rubart Michael; Vatta Matteo; Everett Thomas H; George Alfred L Jr; Chen Peng Sheng^*

来源：Heart Rhythm, 2016, 13(8): 1716-1723.

DOI：10.1016/j.hrthm.2016.05.009

• Long QT syndrome
• Catecholaminergic polymorphic ventricular tachycardia
• Ion channels
• Patch damp
• Arrhythmias

BACKGROUND Apamin-sensitive small-conductance calcium-activated potassium (SK) channels are gated by intracellular Ca2+ through a constitutive interaction with calmodulin.
OBJECTIVE We hypothesize that arrhythmogenic human calmodulin mutations impede activation of SK channels.
METHODS We studied 5 previously published calmodulin mutations (N54I, N98S, D96V, D130G, and F9OL). Plasmids encoding either wild-type or mutant calmodulin were transiently transfected into human embryonic kidney 293 cells that stably express subtype 2 of SK protein channels (SK2 cells). Whole-cell voltage-damp recording was used to determine apamin-sensitive current densities. We also performed optical mapping studies in normal murine hearts to determine the effects of apamin in hearts with (n=7) or without (n=3) pretreatment with sea anemone toxin.
RESULTS SK2 cells transfected with wild-type calmodulin exhibited an apamin-sensitive current density of 33.6 pA/pF (31.4-36.5 pA/pF) (median and confidence interval 25th-75th percentile), which was significantly higher than that observed for cells transfected with N54I (17.0 pA/pF [14.0-27.7 pA/pF]; P =.016), F9OL (22.6 pA/pF [20.3-24.3 pA/pF]; P =.011), D96V (13.0 pA/pF [10.9-15.8 pA/pF]; P =.003), N98S (13.7 pA/pF [8.8-20.4 pA/pF]; P =.005), and D130G (17.6 pA/pF [13.8-24.6 pA/pF]; P =.003). The decrease in SK2 current densities was not associated with a decrease in membrane protein expression or intracellular distribution of the channel protein. Apamin increased the ventricular action potential duration at 80% repolarization (from 79.6 ms [63.4-93.3 ms] to 121.8 ms [97.9-127.2 ms]; P =.010) in hearts pretreated with anemone toxin but not in control hearts.
CONCLUSION Human arrhythmogenic calmodulin mutations impede the activation of SK2 channels in human embryonic kidney 293 cells.

• 出版日期2016-8
• 单位西北大学