Skeletal muscle L-type Ca2+ current modulation in γ1-deficient and wildtype murine myotubes by the γ1 subunit and cAMP
Skeletal muscle L-type Ca2+ current modulation in γ1-deficient and wildtype murine myotubes by the γ1 subunit and cAMP
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DOI：
10.1113/jphysiol.2001.012745
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发表时间：
2002-03-01
影响因子：
5.5
通讯作者：
Flockerzi, V
中科院分区：
文献类型：
--
作者：
Held, B;Freise, D;Flockerzi, V
用全细胞膜片钳技术研究了小鼠骨骼肌L型钙通道γ 1亚基对稳态失活和电流幅度的调节作用。γ 1亚基的瞬时表达，但不是γ 2（stargazin）蛋白，在原代培养的肌管从γ 1缺陷小鼠的稳态失活移动约-15 mV，从而恢复野生型（WT）的稳态失活和电流幅度。在4周及以上的动物的肌管中，γ 1缺陷细胞中增加的Ca 2+电流幅度被取消，而稳态失活的正向转变与小鼠年龄无关。使用膜渗透类似物8-Br-cAMP提高细胞内cAMP水平导致WT细胞中Ca 2+电流幅度增加至γ 1缺陷型肌管中的水平。在γ 1缺陷细胞的电流幅度或在任一基因型的稳态失活没有影响。Rp-cAMPS是cAMP依赖性蛋白激酶的竞争性抑制剂，对WT Ca 2+电流幅度和稳态失活没有影响，但在γ 1缺陷型肌管中降低了电流幅度，而不影响这些细胞的稳态失活。这些数据表明，由于右移稳态失活和增加的L型Ca 2+电流幅度，在缺乏γ 1亚基的肌管中增加的Ca 2+内流由γ 1亚基决定。对电流幅度的影响取决于小鼠的年龄，其cAMP依赖性调制似乎由γ 1亚基控制。
Modulation of the steady-state inactivation and current amplitude by the gamma1 subunit of the murine skeletal muscle L-type Ca2+ channel were investigated using the whole-cell patch-clamp technique. Transient expression of the gamma1 subunit, but not of the gamma2 (stargazin) protein, in primary cultured myotubes from gamma1-deficient mice shifted the steady-state inactivation approximately -15 mV, thereby restoring wildtype (WT) steady-state inactivation and current amplitude. The increased Ca2+ current amplitude in gamma1-deficient cells was abolished in myotubes from animals of 4 weeks and older whereas the positive shift in steady-state inactivation was independent of mouse age. Raising intracellular cAMP levels using the membrane-permeant analogue 8-Br-cAMP led to an increase in Ca2+ current amplitude in WT cells to the level in gamma1-deficient myotubes. There was no effect on the current amplitude in gamma1-deficient cells or on the steady-state inactivation in either genotype. Rp-cAMPS, a competitive inhibitor of cAMP-dependent protein kinase, had no effect on the WT Ca2+ current amplitude and steady-state inactivation, but diminished the current amplitude in gamma1-deficient myotubes without affecting the steady-state inactivation in these cells. These data show that the increased Ca2+ influx in myotubes lacking the gamma1 subunit, due to right-shifted steady-state inactivation and increased L-type Ca2+ current amplitude, is determined by the gamma1 subunit. The effect on current amplitude depends on the age of the mice and its cAMP-dependent modulation appears to be controlled by they gamma1 subunit.