Nieto-Marín Paloma, Jiménez-Jáimez Juan, Tinaquero David, Alfayate Silvia, Utrilla Raquel G, Rodríguez Vázquez Del Rey María Del Mar, Perin Francesca, Sarquella-Brugada Geòrgia, Monserrat Lorenzo, Brugada Josep, Tercedor Luis, Tamargo Juan, Delpón Eva, Caballero Ricardo
Departamento de Farmacología, Facultad de Medicina, Universidad Complutense de Madrid, Instituto de Investigación Sanitaria Gregorio Marañón, CIBERCV, Madrid, Spain.
Unidad de Arritmias, Hospital Universitario Virgen de las Nieves, Instituto de Investigación Biosanitaria de Granada, Granada, Spain.
Rev Esp Cardiol (Engl Ed). 2019 Apr;72(4):324-332. doi: 10.1016/j.rec.2018.03.012.
A known long QT syndrome-related mutation in Nav1.5 cardiac channels (p.R1644H) was found in 4 members of a Spanish family but only 1 of them showed prolongation of the QT interval. In the other 3 relatives, a novel missense mutation in Cav1.2 cardiac channels was found (p.S1961N). Here, we functionally analyzed p.S1961N Cav1.2 channels to elucidate whether this mutation regulates the expressivity of the long QT syndrome phenotype in this family.
L-type calcium current (I) recordings were performed by using the whole-cell patch-clamp technique in Chinese hamster ovary cells transiently transfected with native and/or p.S1961N Cav1.2 channels.
Expression of p.S1961N channels significantly decreased I density. Using Ba as a charge carrier to suppress the Ca-dependent inactivation of Cav1.2 channels, we demonstrated that the mutation significantly accelerates the voltage-dependent inactivation of Cav1.2 channels decreasing the inactivation time constant. As a consequence, the total charge flowing through p.S1961N Cav1.2 channels significantly decreased. The effects of the p.S1961N Cav1.2 and p.R1644H Nav1.5 mutations alone or their combination on the action potential (AP) morphology were simulated using a validated model of the human ventricular AP. The p.S1961N Cav1.2 mutation shortens the AP duration and abrogates the prolongation induced by p.R1644H Nav1.5 channels.
The p.S1961N mutation in Cav1.2 channels decreased the I, an effect which might shorten ventricular AP. The presence of the loss-of-function Cav1.2 mutation could functionally compensate the prolonging effects produced by the Nav1.5 gain-of-function mutation.
在一个西班牙家庭的4名成员中发现了一种已知的与长QT综合征相关的Nav1.5心脏通道突变（p.R1644H），但其中只有1人表现出QT间期延长。在另外3名亲属中，发现了心脏Cav1.2通道的一种新的错义突变（p.S1961N）。在此，我们对p.S1961N Cav1.2通道进行了功能分析，以阐明该突变是否调节了这个家庭中长QT综合征表型的表达。
采用全细胞膜片钳技术，在瞬时转染了天然和/或p.S1961N Cav1.2通道的中国仓鼠卵巢细胞中记录L型钙电流（I）。
p.S1961N通道的表达显著降低了I密度。使用Ba作为电荷载体来抑制Cav1.2通道的钙依赖性失活，我们证明该突变显著加速了Cav1.2通道的电压依赖性失活，降低了失活时间常数。因此，通过p.S1961N Cav1.2通道流动的总电荷量显著减少。使用经过验证的人心室动作电位（AP）模型，模拟了p.S1961N Cav1.2和p.R1644H Nav1.5突变单独或联合对动作电位（AP）形态的影响。p.S1961N Cav1.2突变缩短了动作电位持续时间，并消除了p.R1644H Nav1.5通道诱导的延长。
Cav1.2通道中的p.S1961N突变降低了I，这种效应可能会缩短心室动作电位。功能丧失的Cav1.2突变的存在可能在功能上补偿Nav1.5功能获得性突变产生的延长效应。
