Calmodulin reverses rundown of L-type Ca(2+) channels in guinea pig ventricular myocytes.
Calmodulin reverses rundown of L-type Ca(2+) channels in guinea pig ventricular myocytes.
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DOI：
10.1152/ajpcell.00105.2004
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发表时间：
2004-12
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影响因子：
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通讯作者：
Jianjun Xu;L. Hao;A. Kameyama;M. Kameyama
中科院分区：
文献类型：
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作者：
Jianjun Xu;L. Hao;A. Kameyama;M. Kameyama
钙调素（CaM）作为Ca（2+）感受器参与Ca（2+）通道的调节。在豚鼠心室肌细胞上观察了钙调素（CaM）对L型钙（2+）通道的作用。Ca（2+）通道活性在1-3分钟内消失，当将贴片切除并暴露于人工细胞内溶液时，不再出现。然而，应用钙调素（0.03，0.3，3 μ M）+ 3 mM ATP的细胞内溶液1分钟内补丁切除导致剂量依赖性激活通道活性。通道活性平均分别为细胞附着模式的11.2%、94.7%和292.9%。在纳摩尔浓度（[Ca（2+）]）下，CaM + ATP可诱导通道内面向外的膜片钳模式的通道活动，而当[Ca（2+）]增加到微摩尔浓度时，通道活动迅速失活，表明CaM对通道的作用是Ca（2+）依赖性的。在斑片切除后2、4、6、8和10分钟，CaM（0.75 μ M）+ ATP分别诱导Ca（2+）通道活性达到150%、100%、96.9%、29.3%和16.6%，表明CaM对通道的作用具有时间依赖性。添加有腺苷5 '-（β，γ-亚氨基）三磷酸（AMP-PNP）的CaM也诱导通道活性，尽管效力低得多且持续时间短。蛋白激酶抑制剂KN-62、CaM依赖性蛋白激酶（CaMK）II 281-309、autocamtide-related CaMK II抑制肽和K252 a（各1-10 μ M）不阻断CaM的作用，表明CaM对Ca（2+）通道的作用是磷酸化非依赖性的。单独的CaM和ATP都不能诱导Ca（2+）通道活性，表明CaM和ATP对Ca（2+）通道有协同作用。这些结果表明，CaM是Ca（2+）通道基础活性的重要调节因子。
Calmodulin (CaM) is implicated in regulation of Ca(2+) channels as a Ca(2+) sensor. The effect of CaM on rundown of L-type Ca(2+) channels in inside-out patch form was investigated in guinea pig ventricular myocytes. Ca(2+) channel activity disappeared within 1-3 min and did not reappear when the patch was excised and exposed to an artificial intracellular solution. However, application of CaM (0.03, 0.3, 3 microM) + 3 mM ATP to the intracellular solution within 1 min after patch excision resulted in dose-dependent activation of channel activity. Channel activity averaged 11.2%, 94.7%, and 292.9%, respectively, of that in cell-attached mode. Channel activity in inside-out patch mode was induced by CaM + ATP at nanomolar Ca(2+) concentrations ([Ca(2+)]); however, increase to micromolar [Ca(2+)] rapidly inactivated the channel activity induced, revealing that the effect of CaM on the channel was Ca(2+) dependent. At the 2nd, 4th, 6th, 8th, and 10th minutes after patch excision, CaM (0.75 microM) + ATP induced Ca(2+) channel activity to 150%, 100%, 96.9%, 29.3%, and 16.6%, respectively, revealing a time-dependent action of CaM on the channel. CaM added with adenosine 5'-(beta,gamma-imido)triphosphate (AMP-PNP) also induced channel activity, although with much lower potency and shorter duration. Protein kinase inhibitors KN-62, CaM-dependent protein kinase (CaMK)II 281-309, autocamtide-related CaMKII inhibitor peptide, and K252a (each 1-10 microM) did not block the effect of CaM, indicating that the effect of CaM on the Ca(2+) channel was phosphorylation independent. Neither CaM nor ATP alone induced Ca(2+) channel activity, showing a cooperative effect of CaM and ATP on the Ca(2+) channel. These results suggest that CaM is a crucial regulatory factor of Ca(2+) channel basal activity.