Targeted inhibition of cardiomyocyte Gi signaling enhances susceptibility to apoptotic cell death in response to ischemic stress
Targeted inhibition of cardiomyocyte Gi signaling enhances susceptibility to apoptotic cell death in response to ischemic stress
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DOI：
10.1161/circulationaha.107.752618
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发表时间：
2008-03-18
期刊：
影响因子：
37.8
通讯作者：
Koch, Walter J.
中科院分区：
文献类型：
--
作者：
DeGeorge, Brent R., Jr.;Gao, Erhe;Koch, Walter J.
背景：功能失调心肌进展为心力衰竭的一个显著特征是腺苷酸环化酶抑制鸟嘌呤核苷酸(G)蛋白α亚基（G α）的上调（i2）。在体内，心脏中增加的Gi活性是有益的还是有害的，还没有最终确定。Gi信号传导与心脏保护剂的作用机制有关；然而，没有活体证据表明任何G α亚基具有心脏保护作用。我们创造了一种新的分子工具，专门研究Gi蛋白在正常和功能失调心肌中的作用。方法和结果：我们开发了一类特异性的Gi抑制剂肽，GiCT，由G α (i2)区域组成，与G蛋白偶联受体特异性相互作用。GiCT在体内和体外均能特异性抑制Gi信号，而Gs和Gq信号不受影响。GiCT在转基因小鼠体内的表达有效地导致心脏G α (i2)信号的“功能性敲除”。可诱导的心脏特异性GiCT转基因小鼠显示出与非转基因小鼠一致的基线表型。然而，当遭受缺血/再灌注损伤时，与非转基因小鼠相比，GiCT转基因小鼠的梗死面积显著增加（从36.9 +/- 2.5%增加到50.9 +/- 4.3%）。在机制上，这种缺血/再灌注后表型包括心肌凋亡增加和由此导致的收缩性能下降。结论：总的来说，我们的研究结果证明了GiCT在体内的应用，可以揭示应激心肌中Gi信号传导的特定机制。我们使用GiCT的结果表明，G α (i2)的上调是缺血后保护肌细胞免于凋亡的适应性保护反应。
Background-A salient characteristic of dysfunctional myocardium progressing to heart failure is an upregulation of the adenylyl cyclase inhibitory guanine nucleotide (G) protein alpha subunit, G alpha(i2). It has not been determined conclusively whether increased Gi activity in the heart is beneficial or deleterious in vivo. Gi signaling has been implicated in the mechanism of cardioprotective agents; however, no in vivo evidence exists that any of the G alpha subunits are cardioprotective. We have created a novel molecular tool to specifically address the role of Gi proteins in normal and dysfunctional myocardium.Methods and Results-We have developed a class-specific Gi inhibitor peptide, GiCT, composed of the region of G alpha(i2) that interacts specifically with G protein-coupled receptors. GiCT inhibits Gi signals specifically in vitro and in vivo, whereas Gs and Gq signals are not affected. In vivo expression of GiCT in transgenic mice effectively causes a " functional knockout" of cardiac G alpha(i2) signaling. Inducible, cardiac-specific GiCT transgenic mice display a baseline phenotype consistent with nontransgenic mice. However, when subjected to ischemia/reperfusion injury, GiCT transgenic mice demonstrate a significant increase in infarct size compared with nontransgenic mice (from 36.9 +/- 2.5% to 50.9 +/- 4.3%). Mechanistically, this post-ischemia/reperfusion phenotype includes increased myocardial apoptosis and resultant decreased contractile performance.Conclusions-Overall, our results demonstrate the in vivo utility of GiCT to dissect specific mechanisms attributed to Gi signaling in stressed myocardium. Our results with GiCT indicate that upregulation of G alpha(i2) is an adaptive protective response after ischemia to shield myocytes from apoptosis.