PHOSPHORYLATION OF C-PROTEIN, TROPONIN-I AND PHOSPHOLAMBAN IN ISOLATED RABBIT HEARTS
PHOSPHORYLATION OF C-PROTEIN, TROPONIN-I AND PHOSPHOLAMBAN IN ISOLATED RABBIT HEARTS
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DOI：
10.1042/bj2490709
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发表时间：
1988-02-01
影响因子：
4.1
通讯作者：
SOLARO, RJ
中科院分区：
文献类型：
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作者：
GARVEY, JL;KRANIAS, EG;SOLARO, RJ
在Langendorff灌流的兔心脏进行各种变力性干预的肌原纤维和骶浆网（SR）蛋白的磷酸化进行了研究。用异丙肾上腺素刺激心脏导致肌钙蛋白I（TnI）和C-蛋白在肌原纤维和受磷蛋白在SR中的磷酸化。受磷蛋白的磷酸化可以通过用无药物缓冲液灌注15分钟来逆转，用异丙肾上腺素脉冲灌注1分钟后，此时异丙肾上腺素刺激的机械效应也被逆转。然而，TnI和C蛋白在此时仍保持磷酸化。此外，抑制钙激活的镁依赖性ATP酶（Mg-ATP酶）的活性与肌原纤维磷酸化持续从心脏冷冻后15分钟的异丙肾上腺素洗脱制备的肌原纤维。为了评估C蛋白磷酸化在降低Ca 2+激活肌原纤维Mg-ATP酶活性中的作用，我们重建了一个受调节的肌动球蛋白系统，其中只有C蛋白被磷酸化。在这个系统中，C-蛋白磷酸化没有贡献的Mg-ATP酶活性的Ca 2+激活的减少，表明肌钙蛋白I磷酸化是负责降低肌原纤维对Ca 2+的敏感性。这些观察结果支持如下假设：受磷蛋白磷酸化在哺乳动物心脏对β-受体激动剂的机械响应中比TnI或C-蛋白磷酸化起更主要的作用。肾上腺素能刺激
Phosphorylation of myofibrillar and sacroplasmic-reticulum (SR) proteins was studied in Langendorff-perfused rabbit hearts subjected to various inotropic interventions. Stimulation of hearts with isoprenaline resulted in the phosphorylation of both troponin I (TnI) and C-protein in myofibrils and phospholamban in SR. Phosphorylation of phospholamban could be reversed by a 15 min perfusion with drug-free buffer, after a 1 minute pulse perfusion with isoprenaline, at which time the mechanical effects of isoprenaline stimulation had also been reversed. However, both TnI and C-protein remained phosphorylated at this time. Moreover, the inhibition of Ca2+ activation of the Mg2-dependent ATPase (Mg-ATPase) activity associated with myofibrillar phosphorylation persisted in myofibrils prepared from hearts frozen after 15 min of washout of isoprenaline. To assess the contribution of C-protein phosphorylation in the decrease of Ca2+ activation of themyofibrillar Mg-ATPase activity, we reconstituted a regulated actomyosin system in which only C-protein was phosphorylated. In this system, C-protein phosphorylation did not contribute to the decrease in Ca2+ activation of Mg-ATPase activity, indicating that TnI phosphorylation is responsible for the diminished sensitivity of the myofibrils to Ca2+. These observations support the hypothesis that phospholamban phosphorylation plays a more dominant role than TnI or C-protein phosphorylation in the mechanical response of the mammalian heart to .beta.-adrenergic stimulation.