AKAP150信号通路在压力超负荷引起小鼠心肌重构的作用及机制

Impaired Ca2+ cycling and myocyte contractility are a hallmark of heart failure triggered by pathological stress such as hemodynamic overload，however, the molecular mechanisms that regulate Impaired Ca2+ cycling in the heart and its physiological relevance in myocardial remodeling and heart failure remain largely unknown.The A-Kinase anchoring protein AKAP150 has been shown to play a role in regulation of Ca2+ cycling and excitation–contraction in cardiomyocytes. Here we examined how AKAP150 signalling complexes impact Ca2+ cycling, myocyte contractility, and heart failure susceptibility following pressure overload. We detected a significant reduction of AKAP150 expression in the failing wild-type mouse heart induced by pressure overload. Importantly, cardiac-specific AKAP150 knockout mice were predisposed to develop dilated cardiomyopathy with severe cardiac dysfunction, fibrosis and reduction of TAK1 expression after pressure overload. In contrast, AKAP150 transgenic mice enhance TAK1 activity, show less pathological remodelling and heart failure progression induced by overload. Isopreterenol-induced Ca2+ cycling also activates TAK1 and enhances the expression of AKAP150 significantly. Mechanistically, our hypothesis is that AKAP150 regulate Ca2+cycling and myocyte contractility following adrenergic stimulation or pressure overload via TAK1 pathway. Here we propose an investigation of the novel function of AKAP150 in regulating cell calcium transit and heart failure propensity both in vivo and in vitro. We will implement a series of innovative genetic, molecular, and functional approaches to identify AKAP150/TAK1 signaling mechanisms underlying cardiac remodeling and heart failure. The biology surrounding the AKAP150 signaling network is novel and innovative, and will likely uncover new mechanistic perspectives from which heart failure can be approached therapeutically.

心肌细胞钙离子浓度失调可导致心脏功能结构异常等疾病的发生。如何调控压力超负荷条件下心肌钙离子异常所致心肌重构的确切分子机制尚未阐明，我们最新报道AKAP150是其中的关键分子。野生小鼠压力超负荷刺激后我们发现AKAP150下降。心脏特异敲除AKAP150小鼠同样压力刺激后心肌细胞钙离子内流速度和心功能显著下降，心室重构加剧，TAK1活性下降，而AKAK150转基因小鼠上述反应得到改善。在体外异苯肾上腺素诱导的心肌细胞钙内流反应中，AKAP15表达升高，TAK1的活性明显升高。我们推测压力超负荷下AKAP150通过激活TAK1而延缓心肌重构和心力衰竭。我们拟采用小鼠压力超负荷以及体外心肌细胞钙离子梯度紊乱模型，观察AKAP150表达变化对钙信号、细胞钙调蛋白及TAK1相关信号分子影响，明确其在心肌重构中的调控机制和心衰中保护作用。此研究将为理解心肌重构发病机理提供新思路及潜在靶点。

越来越多的研究表明心肌细胞钙离子浓度失调可导致心脏重构，心功能异常等疾病。压力超负荷诱导的心肌细胞钙离子梯度的异常与该条件下引发的心肌重构的确切相关机制尚未明了。我们通过本课题进一步明确了AKAP150作为一个支架蛋白在其中发挥了关键调控作用。WT小鼠行升主动脉缩窄造成压力超负荷模型后我们发现AKAP150表达下降，进一步研究发现在心脏特异敲除AKAP150小鼠压力超负荷刺激后心肌细胞钙离子内流速度和心功能显著下降，心脏重构加剧，TAK1表达下降，在AKAK150高表达小鼠上述不良反应得到缓解。为了进一步明确AKAK150通过调控TAK1来作用于压力刺激下的心肌重构，我们在体内外诱导心肌肥大模型中发现，TAK1参与心肌细胞钙内流反应异常和AKAP15表达调控；利用体内外心肌肥大模型也发现压力超负荷诱导TAK1激活后，AKAP150与RYR2、SERCA2、PKA和PLN等钙调蛋白结合。在实际课题进展过程中，我们有了一些阶段性的结论：心肌细胞中AKAP150先后招募并形成PLN-SERCA2-RYR2-AKAP150和AKAP150-PKA-TAK1复合体，由于AKAP150的支架作用使上述蛋白分子空间上靠近发生相互作用后激活对应靶激酶，进而起调节心肌细胞内钙离子浓度，最终影响心脏重构的发生发展。此项研究还将继续深入TAK1参与AKAP150信号通路中压力超负荷引起的心肌重构中发挥的重要作用和相关分子机制研究。截止目前，该项研究已经发表受本项目资助SCI论文5篇，培养硕士研究生3名，博士生1名。

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