The Autonomic Nervous System Regulates the Heart Rate through cAMP-PKA Dependent and Independent Coupled-Clock Pacemaker Cell Mechanisms
The Autonomic Nervous System Regulates the Heart Rate through cAMP-PKA Dependent and Independent Coupled-Clock Pacemaker Cell Mechanisms
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DOI：
10.3339/fphys.2016.00419
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发表时间：
2016-09-27
影响因子：
4
通讯作者：
Yaniv, Yael
中科院分区：
文献类型：
--
作者：
Behar, Joachim;Ganesan, Ambhighainath;Yaniv, Yael
窦房结细胞（SANCs）产生控制心率的自发动作电位（APs）。通过自主神经系统，大脑通过刺激激活（肾上腺素能）或灭活（胆碱能）腺苷酸环化酶（AC）的膜受体来调节SANG自动性。然而，这些相反的事件并不是简单的相加。我们发现肾上腺素能信号的激活增加了AC-CAMP/PKA信号，这介导了SANG AP放电速率的增加（即正变时调节）。然而，对于胆碱能受体之间的串音和SANC - AP放电速率的降低（即负变时调节）所涉及的内在起搏器机制的理解有限。我们假设AC-cAMP/PKA活性的变化对于介导AP发射速率的降低或增加至关重要，并且速率的变化是由于内部和膜机制。在被表达FRET传感器AKAR3的腺病毒感染的培养的成年兔起搏器细胞中，PKA活性和AP发射率在肾上腺素能受体刺激（异丙肾上腺素，ISO）或胆碱能刺激（胆碱醇，CCh）的反应中紧密相关。为了确定介导PKA信号和起搏器功能之间的主要分子靶点，我们建立了一个机制计算模型。该模型包括对自主神经受体、翻译后信号级联、膜分子和内部起搏器机制的描述。模型模拟的结果与实验结果相似，忠实地再现了响应CCh或ISO或两者的组合（即强化拮抗）时AP发射速率的变化。消除AC-cAMP-PKA信号消除了自主受体刺激对AP放电速率的核心作用。具体来说，禁用磷蛋白对SERCA活性的调节导致CCh的作用显著降低，并且在ISO刺激下无法增加AP发射速率。直接激活内部起搏器机制导致与脑受体刺激相关的AP放电率发生类似程度的变化。因此，Ca2+和cAMP/ pka依赖性磷酸化限制了自发AP放电速率随时间变化的速率和幅度。
Sinoatrial nodal cells (SANCs) generate spontaneous action potentials (APs) that control the cardiac rate. The brain modulates SANG automaticity, via the autonomic nervous system, by stimulating membrane receptors that activate (adrenergic) or inactivate (cholinergic) adenylyl cyclase (AC). However, these opposing afferents are not simply additive. We showed that activation of adrenergic signaling increases AC-CAMP/PKA signaling, which mediates the increase in the SANG AP firing rate (i.e., positive chronotropic modulation). However, there is a limited understanding of the underlying internal pacemaker mechanisms involved in the crosstalk between cholinergic receptors and the decrease in the SANC AP firing rate (i.e., negative chronotropic modulation). We hypothesize that changes in AC-cAMP/PKA activity are crucial for mediating either decrease or increase in the AP firing rate and that the change in rate is due to both internal and membrane mechanisms. In cultured adult rabbit pacemaker cells infected with an adenovirus expressing the FRET sensor AKAR3, PKA activity and AP firing rate were tightly linked in response to either adrenergic receptor stimulation (by isoproterenol, ISO) or cholinergic stimulation (by carbachol, CCh). To identify the main molecular targets that mediate between PKA signaling and pacemaker function, we developed a mechanistic computational model. The model includes a description of autonomic-nervous receptors, post- translation signaling cascades, membrane molecules, and internal pacemaker mechanisms. Yielding results similar to those of the experiments, the model simulations faithfully reproduce the changes in AP firing rate in response to CCh or ISO or a combination of both (i.e., accentuated antagonism). Eliminating AC-cAMP-PKA signaling abolished the core effect of autonomic receptor stimulation on the AP firing rate. Specifically, disabling the phospholamban modulation of the SERCA activity resulted in a significantly reduced effect of CCh and a failure to increase the AP firing rate under ISO stimulation. Directly activating internal pacemaker mechanisms led to a similar extent of changes in the AP firing rate with respect to brain receptor stimulation. Thus, Ca2+ and cAMP/PKA-dependent phosphorylation limits the rate and magnitude of chronotropic changes in the spontaneous AP firing rate.