Distinct roles of CaM and Ca(2+)/CaM -dependent protein kinase II in Ca(2+) -dependent facilitation and inactivation of cardiac L-type Ca(2+) channels.
Distinct roles of CaM and Ca(2+)/CaM -dependent protein kinase II in Ca(2+) -dependent facilitation and inactivation of cardiac L-type Ca(2+) channels.
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DOI：
10.2170/physiolsci.rp000507
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发表时间：
2007-06
期刊：
影响因子：
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通讯作者：
H. Nie;L. Hao;Jianjun Xu;Etsuko Minobe;A. Kameyama;M. Kameyama
中科院分区：
文献类型：
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作者：
H. Nie;L. Hao;Jianjun Xu;Etsuko Minobe;A. Kameyama;M. Kameyama
L型Ca（2+）通道对细胞内Ca（2+）浓度的增加有两种相反的自动调节反馈形式，即Ca（2+）依赖性易化（CDF）和Ca（2+）依赖性失活（CDI）。钙调素（CaM）已被报道介导的两个反馈。虽然CaM的直接结合和Ca（2+）/CaM -依赖性蛋白激酶II（CaMKII）介导的磷酸化已被认为是潜在的机制，但详细的特征仍有待澄清。在这项研究中，我们研究了CaM和CaMKII抑制剂对CDF和CDI的豚鼠心室肌细胞膜片钳细胞贴附记录。我们证实了高K（+）和高Ca（2）（+）可诱导细胞内Ca（2+）浓度升高，随后产生CDF和CDI。然后，我们发现CDF和CDI都被抑制，并最终被取消与钙调素抑制剂氯丙嗪（1-100 μ M）以浓度依赖性的方式处理。另一种钙调素拮抗剂calmidazolium（1 μ M）显示出类似的效果。相比之下，CaMKII抑制剂KN-62（0.1-3 μ M）和autocamtide 2相关抑制肽（1 μ M）显著延迟CDF和CDI的发展，但它们不抑制CDF或CDI。这些结果表明，钙调素是必要的，可能是足够的两种机制。我们提出了一个假设，即CaM是将Ca（2+）信号分支到CDF和CDI的关键分子，CaMKII在这两者中起着调节作用。
L-type Ca(2+) channels have two opposing forms of autoregulatory feedback, Ca(2+) -dependent facilitation (CDF) and Ca(2+) -dependent inactivation (CDI), in response to increases in intracellular Ca(2+) concentration. Calmodulin (CaM) has been reported to mediate the two feedbacks. Although both the direct binding of CaM and the phosphorylation mediated by Ca(2+)/CaM -dependent protein kinase II (CaMKII) have been suggested as underlying mechanisms, the detailed features remain to be clarified. In this study, we investigated the effects of CaM and CaMKII inhibitors on CDF and CDI with patch clamp cell-attached recordings in guinea-pig ventricular myocytes. We confirmed that a high-K(+) and high-Ca(2)(+) could induce an increase of the intracellular Ca(2+) concentration and subsequent CDF and CDI. We then found that CDF and CDI were both depressed and were finally abolished by treatment with a CaM inhibitor chlorpromazine (1-100 microM) in a concentration-dependent manner. Another CaM antagonist calmidazolium (1 microM) showed a similar effect. In contrast, CaMKII inhibitors, KN-62 (0.1-3 microM) and autocamtide 2 -related inhibitory peptide (1 microM), delayed the development of CDF and CDI significantly, but they did not depress either CDF or CDI. These results imply that CaM is necessary and possibly sufficient for the two mechanisms. We propose a hypothesis that CaM is a key molecule to bifurcate the Ca(2+) signal to CDF and CDI and that CaMKII plays a modulatory role in them both.