Cav1.4α1 subunits can form slowly inactivating dihydropyridine-sensitive L-type Ca2+ channels lacking Ca2+-dependent inactivation
Cav1.4α1 subunits can form slowly inactivating dihydropyridine-sensitive L-type Ca2+ channels lacking Ca2+-dependent inactivation
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DOI：
10.1523/jneurosci.23-14-06041.2003
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发表时间：
2003-07-09
影响因子：
5.3
通讯作者：
Striessnig, J
中科院分区：
文献类型：
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作者：
Koschak, A;Reimer, D;Striessnig, J
神经元L型钙通道Ca（v）1.2 α 1和Ca（v）1.3 α 1在功能上是不同的。Ca（v）1.3alpha1在较低电压下激活，比Ca（v）1.2alpha1失活更慢，使其适合支持持续的L型Ca 2+内向电流（I-Ca、I-L）并用于起搏器功能。我们使用全细胞膜片钳技术比较了人视网膜Ca（v）1.4alpha1在tsA-201细胞中与其他L型alpha 1亚基异源表达后的生物物理学和药理学特性。Ca（v）1.4 α 1介导的内向Ba 2+电流（I-Ba）需要α 2 δ 1和β 3或β 2a亚基的共表达，并且在比Ca（v）1.3 α 1低的转染细胞中检测到。I-Ba在比Ca（v）1.2 α 1更负的电压（5%激活阈值;-39 mV; 15 mM Ba 2+）下激活，并且比Ca（v）1.3 α 1稍正。I-Ba的电压依赖性失活比Ca（v）1.2 α 1和Ca（v）1.3 α 1慢（类似于5秒后50%失活; α 2 δ 1 + β 3共表达）。失活没有增加与Ca 2+作为电荷载体，表明不存在Ca 2+依赖性失活。Ca（v）1.4alpha1在强去极化脉冲作用下表现出电压依赖性、G蛋白非依赖性的易化作用。二氢吡啶（DHP）拮抗剂伊拉地平以电压依赖性方式阻断Ca（v）1.4 α 1，其敏感性比Ca（v）1.2 α 1低15倍。尽管在位置1414（重复IVS 6）处的L型通道特异性酪氨酸残基被苯丙氨酸取代，但发现DHP BayK 8644的强刺激。Ca（v）1.4 α 1 + α 2 δ 1 + β通道复合物可形成具有中等DHP拮抗剂敏感性的LTCC，缺乏Ca 2+依赖性失活。它们的生物物理特性应使它们能够在负电位下促进持续的I-Ca、I-L，例如感觉细胞中的紧张性神经递质释放和尖峰神经元中的平台电位所需的。
The neuronal L-type calcium channels (LTCCs) Ca(v)1.2alpha1 and Ca(v)1.3alpha1 are functionally distinct. Ca(v)1.3alpha1 activates at lower voltages and inactivates more slowly than Ca(v)1.2alpha1, making it suitable to support sustained L-type Ca2+ inward currents (I-Ca,I-L) and serve in pacemaker functions. We compared the biophysical and pharmacological properties of human retinal Ca(v)1.4alpha1 using the whole-cell patch-clamp technique after heterologous expression in tsA-201 cells with other L-type alpha1 subunits. Ca(v)1.4alpha1-mediated inward Ba2+ currents (I-Ba) required the coexpression of alpha2delta1 and beta3 or beta2a subunits and were detected in a lower proportion of transfected cells than Ca(v)1.3alpha1. I-Ba activated at more negative voltages (5% activation threshold; -39mV; 15 mM Ba2+) than Ca(v)1.2alpha1 and slightly more positive than Ca(v)1.3alpha1. Voltage-dependent inactivation of I-Ba was slower than for Ca(v)1.2alpha1 and Ca(v)1.3alpha1 (similar to50% inactivation after 5 sec; alpha2delta1 + beta3 coexpression). Inactivation was not increased with Ca2+ as the charge carrier, indicating the absence of Ca2+-dependent inactivation. Ca(v)1.4alpha1 exhibited voltage-dependent, G-protein-independent facilitation by strong depolarizing pulses. The dihydropyridine (DHP)-antagonist isradipine blocked Ca(v)1.4alpha1 with similar to15-fold lower sensitivity than Ca(v)1.2alpha1 and in a voltage-dependent manner. Strong stimulation by the DHP BayK 8644 was found despite the substitution of an otherwise L-type channel-specific tyrosine residue in position 1414 (repeat IVS6) by a phenylalanine. Ca(v)1.4alpha1 + alpha2delta1 + beta channel complexes can form LTCCs with intermediate DHP antagonist sensitivity lacking Ca2+-dependent inactivation. Their biophysical properties should enable them to contribute to sustained I-Ca,I-L at negative potentials, such as required for tonic neurotransmitter release in sensory cells and plateau potentials in spiking neurons.