β-adrenergic enhancement of sarcoplasmic reticulum calcium leak in cardiac myocytes is mediated by calcium/calmodulin-dependent protein kinase
β-adrenergic enhancement of sarcoplasmic reticulum calcium leak in cardiac myocytes is mediated by calcium/calmodulin-dependent protein kinase
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DOI：
10.1161/01.res.0000258172.74570.e6
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发表时间：
2007-02-16
影响因子：
20.1
通讯作者：
Shannon, Thomas R.
中科院分区：
文献类型：
--
作者：
Curran, Jerald;Hinton, Mark J.;Shannon, Thomas R.
心肌舒张期肌浆网（SR）ryanodine受体的钙泄漏增加可能会减少SR钙含量，并有助于心肌发生。我们测试了β-肾上腺素能受体（β-AR）激动剂是否增加了完整兔心室肌细胞的SR Ca泄漏，以及这是否取决于蛋白激酶A或Ca/钙调蛋白依赖性蛋白激酶II（CaMKII）活性。通过丁卡因对兰尼碱受体的急性阻断和随后Ca从胞质溶胶向SR的转移（在不同频率诱导的各种SR Ca负荷下测量）评估SR Ca泄漏。使用Fluo-4评估细胞溶质[Ca]（[Ca]（i））和SR Ca负荷（[Ca]（SRT））。异丙肾上腺素激活β-AR显著增加SR Ca泄漏。然而，这种作用并没有被H-89阻断蛋白激酶A所抑制，尽管异丙肾上腺素诱导的钙瞬时振幅和[Ca]（i）下降速率的增强预期逆转。相反，CaMKII、KN-93或autocamtide-2相关抑制肽II或β-AR阻断剂逆转了异丙肾上腺素诱导的SR Ca泄漏增强，CaMKII抑制甚至可以将泄漏降低至对照水平以下。Forskolin在激活腺苷酸环化酶和蛋白激酶A时绕过β-AR，尽管Ca瞬时振幅和[Ca]（i）下降速率显著增强，但不增加SR Ca泄漏。结果表明，β-AR刺激以（1）CaMKII依赖性、（2）非蛋白激酶A依赖性和（3）不依赖于体积[Ca]（i）的方式增强舒张期SR Ca泄漏。
Enhanced cardiac diastolic Ca leak from the sarcoplasmic reticulum (SR) ryanodine receptor may reduce SR Ca content and contribute to arrhythmogenesis. We tested whether beta-adrenergic receptor (beta-AR) agonists increased SR Ca leak in intact rabbit ventricular myocytes and whether this depends on protein kinase A or Ca/calmodulin-dependent protein kinase II (CaMKII) activity. SR Ca leak was assessed by acute block of the ryanodine receptor by tetracaine and assessment of the consequent shift of Ca from cytosol to SR (measured at various SR Ca loads induced by varying frequency). Cytosolic [Ca] ([Ca](i)) and SR Ca load ([Ca](SRT)) were assessed using fluo-4. beta-AR activation by isoproterenol dramatically increased SR Ca leak. However, this effect was not inhibited by blocking protein kinase A by H-89, despite the expected reversal of the isoproterenol-induced enhancement of Ca transient amplitude and [Ca](i) decline rate. In contrast, inhibitors of CaMKII, KN-93, or autocamtide-2-related inhibitory peptide II or beta-AR blockade reversed the isoproterenol-induced enhancement of SR Ca leak, and CaMKII inhibition could even reduce leak below control levels. Forskolin, which bypasses the beta-AR in activating adenylate cyclase and protein kinase A, did not increase SR Ca leak, despite robust enhancement of Ca transient amplitude and [Ca](i) decline rate. The results suggest that beta-AR stimulation enhances diastolic SR Ca leak in a manner that is (1) CaMKII dependent, (2) not protein kinase A dependent, and 3) not dependent on bulk [Ca](i).