The cAMP binding protein Epac regulates cardiac myofilament function
The cAMP binding protein Epac regulates cardiac myofilament function
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DOI：
10.1073/pnas.0812536106
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发表时间：
2009-08-18
影响因子：
11.1
通讯作者：
Lezoualc'h, Frank
中科院分区：
文献类型：
--
作者：
Cazorla, Olivier;Lucas, Alexandre;Lezoualc'h, Frank
在心脏中，cAMP是兴奋-收缩偶联的关键调节剂，其生物学效应主要与蛋白激酶A（PKA）的活性有关。本研究的目的是探讨cAMP结合蛋白Epac（由cAMP直接激活的交换蛋白）在调节大鼠心室肌细胞收缩特性中的作用。我们报告，PKA和Epac增加心肌肌节收缩，但通过相反的机制。与PKA类似，cAMP类似物8-（4-chlorophenylthio）-2 '-O-methyl-cAMP（8-pCPT）的选择性Epac激活降低了完整心肌细胞中的Ca 2+瞬时振幅并增加了细胞缩短和透化心肌细胞中的肌丝Ca 2+敏感性。此外，心室肌细胞，这是在体内感染的一个组成型活性形式的Epac，显示增强肌丝钙敏感性相比，对照细胞感染绿色荧光蛋白（GFP）单独。在分子水平上，Epac增加了2种关键肌节蛋白的磷酸化，即心肌肌钙蛋白I（cTnI）和心肌肌球蛋白结合蛋白-C（cMyBP-C）。Epac激活对肌丝Ca 2+敏感性以及对cTnI和cMyBP-C磷酸化的影响不依赖于PKA，并被蛋白激酶C（PKC）和Ca 2+钙调蛋白激酶II（CaMKII）抑制剂阻断。总之，这些发现确定Epac作为一种新的肌丝功能调节剂。
In the heart, cAMP is a key regulator of excitation-contraction coupling and its biological effects are mainly associated with the activity of protein kinase A (PKA). The aim of this study was to investigate the contribution of the cAMP-binding protein Epac (Exchange protein directly activated by cAMP) in the regulation of the contractile properties of rat ventricular cardiac myocytes. We report that both PKA and Epac increased cardiac sarcomere contraction but through opposite mechanisms. Differently from PKA, selective Epac activation by the cAMP analog 8-(4-chlorophenylthio)-2'-O-methyl-cAMP (8-pCPT) reduced Ca2+ transient amplitude and increased cell shortening in intact cardiomyocytes and myofilament Ca2+ sensitivity in permeabilized cardiomyocytes. Moreover, ventricular myocytes, which were infected in vivo with a constitutively active form of Epac, showed enhanced myofilament Ca2+ sensitivity compared to control cells infected with green fluorescent protein (GFP) alone. At the molecular level, Epac increased phosphorylation of 2 key sarcomeric proteins, cardiac Troponin I (cTnI) and cardiac Myosin Binding Protein-C (cMyBP-C). The effects of Epac activation on myofilament Ca2+ sensitivity and on cTnI and cMyBP-C phosphorylation were independent of PKA and were blocked by protein kinase C (PKC) and Ca2+ calmodulin kinase II (CaMKII) inhibitors. Altogether these findings identify Epac as a new regulator of myofilament function.