cAMP-PKA protein kinase is a key nodal signaling pathway that regulates a wide range of heart pacemaker cell functions. These functions are predicted to be involved in regulation of spontaneous action potential (AP) generation of these cells. Here we investigate if the kinetics and stoichiometry of increase in PKA activity match the increase in AP firing rate in response to β-adrenergic receptor (β-AR) stimulation or phosphodiesterase (PDE) inhibition, that alters the AP firing rate of heart sinoatrial pacemaker cells. In cultured adult rabbit pacemaker cells infected with an adenovirus expressing the FRET sensor AKAR3, the EC50 in response to graded increases in the intensity of β-AR stimulation (by Isoproterenol) the magnitude of the increases in PKA activity and the spontaneous AP firing rate were similar (0.4±0.1nM vs. 0.6±0.15nM, respectively). Moreover, the kinetics (t1/2) of the increases in PKA activity and spontaneous AP firing rate in response to β-AR stimulation or PDE inhibition were tightly linked. We characterized the system rate-limiting biochemical reactions by integrating these experimentally derived data into a mechanistic-computational model. Model simulations predicted that phospholamban phosphorylation is a potent target of the increase in PKA activity that links to increase in spontaneous AP firing rate. In summary, the kinetics and stoichiometry of increases in PKA activity in response to a physiological (β-AR stimulation) or pharmacological (PDE inhibitor) stimuli match those of changes in the AP firing rate. Thus Ca(2+)-cAMP/PKA-dependent phosphorylation limits the rate and magnitude of increase in spontaneous AP firing rate.

中文翻译：

---

心脏起搏器细胞中PKA生化信号网络动力学与动作电位激发率之间的实时关系：心脏起搏器细胞中PKA激活的动力学。

cAMP-PKA蛋白激酶是调节广泛范围的心脏起搏器细胞功能的关键节点信号通路。预计这些功能与这些细胞的自发动作电位（AP）生成有关。在这里，我们研究了PKA活性增加的动力学和化学计量是否与响应β-肾上腺素受体（β-AR）刺激或磷酸二酯酶（PDE）抑制而导致AP放电速率的增加相匹配，从而改变了心脏窦房起搏器的AP放电速率细胞。在培养的表达FRET传感器AKAR3的腺病毒感染的成年兔起搏器细胞中，响应于β-AR刺激强度（异丙肾上腺素）的逐步增加，EC50的响应是PKA活性增加的幅度和自发AP发射率相似（0.4±0.1nM与0.6±0.15nM，分别）。此外，响应β-AR刺激或PDE抑制，PKA活性增加的动力学（t1 / 2）和自发AP放电速率紧密相关。我们通过将这些实验得出的数据整合到机械计算模型中来表征系统限速生化反应。模型模拟预测，磷酸lamban磷酸化是PKA活性增加的有效目标，而PKA活性与自发AP发射速率的增加有关。总之，响应于生理学（β-AR刺激）或药理学（PDE抑制剂）刺激，PKA活性增加的动力学和化学计量与AP发射速率的变化相匹配。因此，Ca（2 +）-cAMP / PKA依赖性磷酸化限制了自发AP放电速率的增加速率和幅度。响应β-AR刺激或PDE抑制，PKA活性增加的动力学（t1 / 2）和自发AP发射速率紧密相关。我们通过将这些实验得出的数据整合到机械计算模型中来表征系统限速生化反应。模型模拟预测，磷酸lamban磷酸化是PKA活性增加的有效目标，而PKA活性与自发AP发射速率的增加有关。总之，响应于生理学（β-AR刺激）或药理学（PDE抑制剂）刺激，PKA活性增加的动力学和化学计量与AP发射速率的变化相匹配。因此，Ca（2 +）-cAMP / PKA依赖性磷酸化限制了自发AP放电速率的增加速率和幅度。响应β-AR刺激或PDE抑制，PKA活性增加的动力学（t1 / 2）和自发AP发射速率紧密相关。我们通过将这些实验得出的数据整合到机械计算模型中来表征系统限速生化反应。模型模拟预测，磷酸lamban磷酸化是PKA活性增加的有效目标，而PKA活性与自发AP发射速率的增加有关。总之，响应于生理学（β-AR刺激）或药理学（PDE抑制剂）刺激，PKA活性增加的动力学和化学计量与AP发射速率的变化相匹配。因此，Ca（2 +）-cAMP / PKA依赖性磷酸化限制了自发AP放电速率的增加速率和幅度。