Regulation of cardiac IKs potassium current by membrane phosphatidylinositol 4,5-bisphosphate
Regulation of cardiac IKs potassium current by membrane phosphatidylinositol 4,5-bisphosphate
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DOI：
10.1074/jbc.m409374200
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发表时间：
2004-12-03
影响因子：
4.8
通讯作者：
Matsuura, H
中科院分区：
文献类型：
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作者：
Ding, WG;Toyoda, F;Matsuura, H
采用全细胞膜片钳技术，观察了膜磷脂磷脂酰肌醇4，5-二磷酸(PtdIns(4，5)P-2)对豚鼠心房肌细胞延迟整流钾电流(I-Ks)慢激活成分的调节作用。从-50 mV的保持电位给出去极化电压阶跃，并通过测量2-S去极化至+30 mV后返回保持电位时所诱发的尾电流的幅度来评估不同测试试剂对iKs的影响。通过记录吸管将50微米的Wortmannin注入细胞内，在10-15分钟的时间内，I-K逐渐增加，达到斑片膜破裂后不久获得的初始幅度的208.5+/-14.6%(n=9)。细胞内应用抗PtdIns(4，5)P-2单抗也使IKs的波幅增加到198.4+/-19.9%(n=5)。相反，外源性PtdIns(4，5)P-2在10和100微米的细胞内负荷后，I-K波幅分别下降到54.3+/-3.8%(n=5)和44.8+/-8.2%(n=5)。细胞内应用新霉素(50 MU)或铝(50 MU)后，I-K波幅分别增加到161.0+/-13.5%(n=4)和150.0+/-8.2%(n=4)。这些结果有力地表明内源性膜PtdIns(4，5)P-2通过与PtdIns(4，5)P-2上带负电荷的头部基团的静电相互作用抑制I-Ks通道。加入PtdIns(4，5)P-2后，PtdIns(4，5)P-2对P2Y受体刺激的I-Ks的增强作用几乎完全消失，提示膜PtdIns(4，5)P-2的耗竭参与了P2Y受体刺激对I-Ks的增强作用。因此，膜PtdIns(4，5)P-2可能是豚鼠心房肌细胞I-Ks的重要生理调节因子。
Regulation of the slowly activating component of delayed rectifier K+ current (I-Ks) by membrane phospholipid phosphatidylinositol 4,5-bisphosphate ( PtdIns( 4,5) P-2) was examined in guinea pig atrial myocytes using the whole-cell patch clamp method. I-Ks was elicited by depolarizing voltage steps given from a holding potential of - 50 mV, and the effect of various test reagents on IKs was assessed by measuring the amplitude of tail current elicited upon return to the holding potential following a 2-s depolarization to + 30 mV. Intracellular application of 50 muM wortmannin through a recording pipette evoked a progressive increase in I-Ks over a 10-15- min period to 208.5 +/- 14.6% (n = 9) of initial magnitude obtained shortly after rupture of the patch membrane. Intracellular application of anti-PtdIns(4,5) P-2 monoclonal antibody also increased the amplitude of IKs to 198.4 +/- 19.9% (n = 5). In contrast, intracellular loading with exogenous PtdIns(4,5) P-2 at 10 and 100 muM produced a marked decrease in the amplitude of I-Ks to 54.3 +/- 3.8% ( n = 5) and 44.8 +/- 8.2% ( n = 5), respectively. Intracellular application of neomycin ( 50 muM) or aluminum ( 50 muM) evoked an increase in the amplitude of I-Ks to 161.0 +/- 13.5% ( n = 4) and 150.0 +/- 8.2% ( n = 4), respectively. These results strongly suggest that I-Ks channel is inhibited by endogenous membrane PtdIns( 4,5) P-2 through the electrostatic interaction with the negatively charged head group on PtdIns(4,5) P-2. Potentiation of I-Ks by P2Y receptor stimulation with 50 muM ATP was almost totally abolished when PtdIns( 4,5) P-2 was included in the pipette solution, suggesting that depletion of membrane PtdIns(4,5) P-2 is involved in the potentiation of I-Ks by P2Y receptor stimulation. Thus, membrane PtdIns( 4,5) P-2 may act as an important physiological regulator of I-Ks in guinea pig atrial myocytes.