Regulation of Gq Signaling in Cardiac Fibroblasts and its Role in Cardiac Remodel

描述(由申请人提供)：心脏成纤维细胞(CF)和心肌细胞(CM)在许多心血管疾病中发生的心脏重构反应中发挥核心作用。它导致CM肥大、CF激活和细胞外基质沉积增加，并经常导致心力衰竭和心律失常。CF作为治疗靶点越来越受到关注，但到目前为止，它们受到的关注比CM少得多。众所周知，GQ信号通路在心脏重构中发挥核心作用，并导致CF的促纤维化作用。然而，对于Cf中GQ信号的调节机制以及Cf中GQ信号如何交叉调节CM和影响血流动力学应激下的心脏重构反应，仍存在着根本的差距。我们最近发现，负GQ调节因子RGS2(G蛋白信号转导调节因子2)在CF中表达，与其他RGS亚型相比，它是唯一对调节敏感的亚型。我们还发现RGS2被cAMP上调，cAMP处于Gs信号通路的中心，具有众所周知的抗纤维化作用。此外，已知cGMP可使RGS2磷酸化，并具有抗纤维化作用。然而，Cf中GQ信号通路的潜在作用机制和潜在的串扰还不是很清楚。这项研究计划的长期目标是促进对GQ信号在CF中的调节及其在确定心脏重构对应激反应中的作用的了解。使用多尺度的实验方法将验证我们的中心假设，即GQ介导的CF信号及其被环核苷酸调节不仅决定CF的反应，而且交叉调节CM功能，从而影响心脏重构。这些研究的具体目的是：(1)确定RGS2作为抗纤维化cAMP效应的介体在成年大鼠心室肌纤维中的作用以及Gs和GQ信号通路之间这种新的串扰的机制；(2)确定在心肌细胞中改变GQ信号对心肌和心脏微组织综合功能反应的影响；(3)确定成纤维细胞限制性RGS2缺失对GQ介导的在体心脏重构的影响。我们将使用心脏微组织和完整的小鼠作为新的实验模型，在这些小鼠中，GQ信号可以在CF中选择性地改变。使用多学科方法，我们将表征结构(纤维化和肥大)和电重构反应，评估收缩功能和心率调节的功能后果，并确定潜在的机制。进一步的创新在于解决了CF-to-CM交叉调节在整体重塑反应中的作用。这项拟议的研究具有重要意义，因为我们将获得关于GQ介导的CF信号、其调控以及由此对CF、CM及其综合重塑反应的后果的新见解，有望有助于开发针对心力衰竭治疗/预防的心脏重塑的新策略。

DESCRIPTION (provided by applicant): Cardiac fibroblasts (CF) and cardiac myocytes (CM) play central roles in the cardiac remodeling response that occurs in many cardiovascular diseases. It entails CM hypertrophy, CF activation and increased extracellular matrix deposition, and often leads to heart failure and arrhythmias. CF increasingly attract attention as therapeutic targets but they have received much less attention than CM so far. The Gq signaling pathway is well known to play a central role in cardiac remodeling and to lead to pro-fibrotic effects in CF. However, there is a fundamental gap in understanding of the mechanisms that regulate Gq signaling in CF and how Gq signaling in CF crossregulates CM and affects the cardiac remodeling response to hemodynamic stress. We recently showed that the negative Gq regulator RGS2 (Regulator of G protein Signaling 2) is expressed in CF and uniquely susceptible to regulation compared to other RGS isoforms. We also show that RGS2 is up- regulated by cAMP, which is at the center of the Gs signaling pathway with well known anti-fibrotic effects. In addition, cGMP is known to phosphorylate RGS2 and also exert anti-fibrotic effects. However, the underlying mechanisms of action and potential crosstalk with the Gq signaling pathway in CF are not yet well understood. The long-term goal of this research program is to advance understanding of the regulation of Gq signaling in CF and its role in determining the cardiac remodeling response to stress. Using multi-scale experimental approaches will test our central hypothesis that Gq-mediated signaling in CF and its regulation by cyclic nucleotides not only determines CF responses but crossregulates CM function and thereby influences cardiac remodeling. The Specific Aims are: (1) To determine the role of RGS2 as a mediator of anti-fibrotic cAMP effects in adult rat ventricular CF and the mechanisms of this novel crosstalk between the Gs and Gq signaling pathways; (2) To determine the effect of altered Gq signaling in CF on CM and the integrated functional response of cardiac microtissues; and (3) To determine the effect of fibroblast-restricted RGS2 deletion on Gq- mediated cardiac remodeling in vivo. We will use cardiac microtissues and intact mice, in which Gq signaling can be selectively altered in CF, as novel experimental models. Using multidisciplinary approaches, we will characterize structural (fibrosis and hypertrophy) and electrical remodeling responses, assess functional consequences on contractile function and heart rate regulation, and determine underlying mechanisms. Further innovation lies in addressing the role of CF-to-CM cross-regulation on the integrated remodeling response. The proposed study is significant, because the new insights we will gain about Gq-mediated signaling in CF, its regulation and the resulting consequences for CF, CM and their integrated remodeling response are expected to aid in the development of new strategies targeting cardiac remodeling for heart failure treatment/prevention.