Regulation of by protein kinases of CFTR chloride current and the acidic pH-activated chloride current in cardiac myocytes

心肌细胞中 CFTR 氯电流和酸性 pH 激活氯电流的蛋白激酶调节

基本信息

批准号：
17500276
负责人：
EHARA Tsuguhisa
金额：
$ 2.39万
依托单位：
Saga University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17500276/
关键词：
Cardiac myocvtes chloride current pH acidic pH-induced current PKA PKC ATP P2-purinergic receptor CFTR P_<2Y>受容体マウス

项目摘要

1. It is well known that extracellular acidosis modulates many types of ion channels in excitable and non-excitable cells. Recently, a novel Cl- current that is activated by acidic pH has been found in rat sertoli cells. A similar current (I_<Cl.pH> was found in ventricular myocytes from mouse and guinea pig. When acidic solution was applied to the cells, I_<Cl.pH> appeared with a delay of 〜1 min, increased gradually, and reached a maximum in 〜5 min. In contrast, the current disappeared rapidly (<1 min) upon resumption of the solution with normal pH (7.4). I_<Cl.pH> was activated in a pH・dependent manner, with a half maximal activation at about pH 6.0. I_<Cl.pH> exhibited a weak time・dependent activation, the current amplitude slightly increasing during depolarizing step pulses. I・V relationship of I_<Cl.pH> showed a strong outward rectification under symmetrical [Cl-] conditions. The anion selectivity of this current was estimated to be I>Cl->Asp. Pharmacological studies showed that I … More _<Cl.pH> was inhibited by several Cl- channel blockers (DIDS, niflumic acid and gliben Cl-amide). Thus, the properties of I_<Cl.pH> differ from those of other cardiac Cl- currents (volume・regulated Cl- current, inwardly rectifying Cl- current, Ca^<2+>・activated Cl- current or CFTR current). I_<Cl.pH> may play a role in the control of the action potential duration under pathological conditions, such as ischemia-related cardiac acidosis.2. The effects of extracellular ATP on β-adrenergic activation of CFTR Cl current (I^<Cl,PKA>) were examined in guinea-pig ventricular cells. The cells were initially exposed to 0.02-1 μM isoproterenol (ISO) for 〜3 min to activate I_<Cl,PKA>, and then to 1.100 μM ATP in the presence of ISO. ATP was found to potentiate I_<Cl,PKA>, in most cells examined. In about 2/<3> of them, however, the potentiation was preceded by an inhibition, I_<Cl,PKA> changing in a biphasic manner. The initial inhibition was due to stimulation of P1-purinoceptor by ATP, since the inhibition was attenuated by the blockers of this receptor type. With 50 μM ATP, the potentiation, on average, resulted in a 1.3 fold increase of the Cl- conductance activated by ISO alone (0.02-1μM). The effects of ADP and ATPγS on I_<Cl,PKA> were similar to those of ATP, while AMP and adenosine never potentiated I_<Cl,PKA>. Thus the potentiation was attributed to a stimulation of P2-purinoceptors. PDBu (0.5 μM), an activator of PKC, facilitated I_<Cl,PKA>, and in the presence of PDBu ATP did not further potentiate I_<Cl,PKA>. When BIM (0.2 μM), an inhibitor of PKC, was present, ATP did not facilitate I_<Cl,PKA>. These findings suggested involvement of PKC in the observed ATP action. When ATP was removed in the presence of ISO, the potentiated ICl,PKA decreased (recovered) only slowly, and, if ATP was reapplied during this slowly recovering phase, the subsequent current potentiation was weak. Thus the stimulation of P_2 purinoceptors by ATP facilitates the β-adrenergic activation of I_<Cl,PKA> through PKC activation, and this potential appears to persist for several min after removal of ATP. Less

1.众所周知，细胞外酸中毒调节可兴奋和不可兴奋细胞中的多种离子通道，最近在大鼠支持细胞中发现了一种由酸性pH激活的新型Cl-电流。在小鼠和豚鼠的心室肌细胞中发现了Cl.pH>，当向细胞施加酸性溶液时，I_<Cl.pH>延迟〜1分钟出现，逐渐增加，并且相比之下，当溶液恢复到正常 pH (7.4) 时，电流迅速消失（<1 分钟），I_<Cl.pH> 以 pH 依赖性方式被激活，半数。在 pH 6.0 左右时，I_<Cl.pH> 表现出弱的时间依赖性激活，在去极化阶跃脉冲期间，电流幅度略有增加，I_<Cl.pH> 在对称下表现出强烈的向外整流。 [Cl-] 条件下，该电流的阴离子选择性估计为 I>Cl->Asp。药理学研究表明，I … 更多 _<Cl.pH> 被多种 Cl- 通道阻滞剂（DIDS、尼氟酸和因此，I_<Cl.pH> 的特性与其他心脏 Cl- 电流（容量、调节 Cl- 电流、内向整流 Cl- 电流、 Ca^<2+>·激活的Cl-电流或CFTR电流）可能在病理条件下（例如缺血相关的心脏酸中毒）的动作电位持续时间的控制中发挥作用。在豚鼠心室细胞中检查细胞外 ATP 对 CFTR Cl 电流 (I^<Cl,PKA>) β-肾上腺素能激活的影响。细胞最初暴露于 0.02-1 μM。异丙肾上腺素 (ISO) 约 3 分钟可激活 I_<Cl,PKA>，然后在存在 ISO 的情况下加入 1.100 μM ATP 可增强 I_<Cl,PKA>，在大多数检查的细胞中。然而，其中的<3>增强之前是抑制，I_<Cl，PKA>以双相方式变化。最初的抑制是由于刺激。 ATP 的 P1-嘌呤受体，因为这种受体类型的阻断剂会减弱抑制作用，因此平均而言，单独使用 ISO (0.02-1μM) 时，增强作用会导致 Cl- 电导增加 1.3 倍。 ADP 和 ATPγS 对 I_<Cl,PKA> 的影响与 ATP 相似，而 AMP 和腺苷从未增强。因此，增强作用归因于 P2-嘌呤受体 (PKC 激活剂) 的刺激，促进 I_<Cl,PKA>，并且在 PDBu 存在下，ATP 不会进一步增强。当存在 PKC 抑制剂 BIM (0.2 μM) 时，ATP 不会促进 I_<Cl,PKA>。这些发现表明存在 I_<Cl,PKA>。观察到的 ATP 作用中的 PKC 当在 ISO 存在的情况下去除 ATP 时，增强的 ICl、PKA 仅缓慢下降（恢复），并且如果在该缓慢恢复阶段重新应用 ATP，则随后的电流增强很弱。 ATP 对 P_2 嘌呤受体的刺激可通过 PKC 激活促进 I_<Cl,PKA> 的 β-肾上腺素能激活，并且这种潜力在去除 ATP 后似乎会持续数分钟。